Category Archives: Comma

ACEA – The importance of oil codes – Comma Technical Bulletin

Are all engine oil manufacturers entitled to make ACEA claims?

According to ACEA (European Automobile Manufacturers’ Association), lubricant marketers or manufacturers making claims according to the ACEA Oil Sequences are required by ACEA to submit a Letter of Conformance to ATIEL (European Lubricants Industry Technical Association). This provides a commitment to develop and manufacture engine lubricants in accordance with the guidelines described in the ATIEL Code of Practice. Comma is a signatory of ATIEL’s code of practice letter of conformance. A list of signatories for both oil marketers and base stock manufacturers can be downloaded from

What are the current ACEA specifications?

ACEA specifications for passenger vehicles are split in two categories, those that are designed for conventional engines (such as ACEA A3/B4) and “catalyst friendly” specifications designed to protect engines fitted with exhaust after-treatment units (such as ACEA C3).

Can specifications for conventional oils be claimed together with “catalyst friendly” specifications?

In the current ACEA specifications the answer is NO. The ACEA 2010 Sequences introduced chemical limits that make ACEA “A/B” and ACEA “C” unsuitable to be claimed together. ACEA “C” classification products are Low SAPS (Sulphated Ash, Phosphorous and Sulphur) engine oils specifically designed to protect Exhaust After-Treatment Units whilst ACEA “A/B” products are only suitable for conventional engines.


Are there different types of ACEA A3/B4? I see some with numbers at the end like A3/B4-04.

The numbers at the end of the ACEA specifications refer to the year the specifications were introduced. This means that A3/ B4-04 does not refer to the current A3/B4 specification but to one that was introduced in 2004. ACEA specifications are regularly updated and as new specifications are introduced, older ones are made obsolete. Although it’s important for oil blenders to know the technical capability of a formulation, strictly speaking the use of a date suffix like this is prohibited. The claim should be represented on the label as A3/B4 and for this to be valid the product in the bottle must meet the current standard. If it doesn’t then no claim should be made at all.


What are the differences between an obsolete speci cation (ACEA A3/B4-04) and the current equivalent?

There are technical differences that make the current version of ACEA A3/B4 higher performance than A3/B4-04. The best way to demonstrate this is to look at the graphs below:


As you can see the current ACEA A3/B4 specification is a higher performance than the equivalent specification in 2004 particularly in soot handling, wear protection, sludge control and piston deposits. The same is also true for ACEA C3. In simple terms, an oil that meets the current ACEA speci cations will outperform an oil that meets the equivalent but older versions.

OEMs sometimes also update their specifications. For example, the bottom graph above shows the major upgrade in requirements of the 2005 review of VW 501 01 specification.

Is there a risk of damage if I’m not using the current specifications?

If the vehicle requires the current ACEA specification then yes!

We make a recommendation based on ACEA A3/B4 for around 7 million vehicles (20%) on the roads today. A product described as ACEA A3/B4-04 may not be suitable for as many as 1 million of those vehicles (about 15%). As legislation has evolved engine design has adapted to accommodate the demands for cleaner and more efficient engines. Smaller, higher revving engines, smaller sump capacities and the increased use of turbochargers and exhaust after-treatment systems are placing more demands on the engine’s oil. Failing to use the right product in your engine can have some very costly consequences so it’s important you are tting the product the manufacturer intended. The engine and warranty could be at risk if you don’t.


Oil thickening and sludge can cause blocked channels and lters within the engine potentially leading to oil starvation, causing damage to the engine. Also, according to BTN Turbo, oil starvation is one of the most common causes of turbocharger failure.

How to get it right?

To be absolutely sure that you are using a product that meets the latest manufacturer’s specifications and avoid the dangers of using products based on obsolete ACEA claims, always use Comma’s website or Workshop Application Guide.

Changing Brake Fluid Technologies – COMMA Technical Bulletin

Brake fluids are becoming more complicated. Why is this?

Vehicle technology has moved on and nowadays the modern passenger car weighs more, accelerates harder and travels substantially faster than its older counterpart. It therefore requires substantially more braking force to bring modern vehicles to a stop. Combined with complex, computer controlled functions such as ABS and ESP, the higher weight and faster speed of modern vehicles makes modern brake systems considerably more demanding on brake uid than they ever were. Modern vehicles therefore need modern, high performance brake uids in order to keep them braking effectively and safely.


Are there any other types of brake fluid?

As well as synthetic PAG-based products there are other types of brake fluid. Mineral oil based products (Comma’s LHM+) have been used in the combined hydraulic systems of Citreons for years. They are designed specifically for this type of application and are not suitable for use where DOT products are specified. They are also not compatible and should never be mixed.


Which brake fluid do I need for my car?

There are a range of products to meet the demands of modern vehicles. Synthetic fluids, based on polyalkylene glycol (PAG), are the most common type (DOT3, DOT4, DOT 4 ESP and DOT 5.1). They are compatible with one another and therefore can be mixed however, as with oil and coolant, you should always comply with the manufacturers’ specifications for the intended vehicle as using the wrong uid can seriously compromise braking performance.

The final type of brake uid is rather confusingly called DOT 5.0 but it should not be confused with the other DOT specified brake fluids as it is completely different technology. DOT 5.0 is a silicon-based product designed for specialist applications, such as racing cars where the fluid is changed after every race. It is not compatible with any other type of brake uid and is not recommended for conventional applications. (Comma doesn’t make a DOT 5.0 fluid which is why the bottle on the picture is grey).


 I’ve heard that brake fluid is hygroscopic. What does that mean? 

Brake fluid is hygroscopic which means that it absorbs water from the air around it hence why you are always advised to start each new brake fluid change with an unopened container of brake fluid.

However, absorbing water is part of the brake fluid’s function. By keeping water locked in tight it stops from pooling in the lower areas of a braking system. This helps to maintain hydraulic pressure, protects against corrosion and maintains the viscosity of the fluid (i.e. it keeps it doing its job). The downside is that as a brake fluid absorbs water its boiling point drops and eventually brake fluid will absorb enough water such that the boiling point becomes dangerously low. This is more or less how the service life of brake fluid is defined.

The brake fluid test

Comma did some testing of their own with a brake fluid tester and the results were quite astonishing. We tested around 750 vehicles and of those approximately 33% were measured at below the 180°C minimum. One was as low as 100°C which is the boiling point of pure water! The risks associated with driving a vehicle with faulty brake fluid are self-evident and compelling. It’s simply not enough to change brake fluid at the same time as faulty discs or pads. Like engine oil or coolant, brake fluid should be changed at the manufacturer’s recommended intervals and at any time in between if it is found to be faulty with a brake fluid boiling point tester.


When do I need to change the brake fluid? 

As the brakes start to heat up temperature of water-contaminated brake fluid approaches and eventually exceeds its boiling point and this causes vapour bubbles to appear. This vapour is very compressible and absorbs large amounts of the force applied to the brake pedal before it ever reaches the callipers, thus making the brakes feel spongy. As the brake fluid gets older, it will continue to absorb more and more water such that the boiling point becomes dangerously low, and so, given the above information, manufacturers always recommend a change of brake fluid at a particular interval (typically between 1 and 2 years).

How to select the right Brake Fluid

To make this increasingly complicated choice a lot easier you can use the Comma Application Guide or our website where you can select your vehicle using the VRN (Vehicle Registration Number) tool or by using the make and model search. Fluid should be changed at the manufacturer’s recommended, you will then be presented with a printable full vehicle recommended product report including engine oil, antifreeze & coolant, transmission oils, brake fluid and greases if applicable.

Ancillary products available from COMMA – COMMA Technical Bulletin

What types of products do you have for ancillaries?

From Air Con Cleaner to Silicone Spray, along with premium quality greases, cleaning products, additives and hand cleaner, Comma stock a range of ancillary products for every job no matter what the size of the workshop or fleet.


What do you mean by additives?

Comma sell two distinct types of additive — those for fuel and those for oil. The engine oil additive is known as Engine Flush and the fuel additives are Diesel Magic, Diesel D-Tox, Petrol Magic and Petrol D-Tox.

What does Engine Flush do?

Comma Engine Flush is a synthetically fortified oil additive, designed to quickly clean the inside of a car or van engine before an oil change. It is designed to be used just before an engine oil change. It is a concentrated charge of detergent additives and will not harm your engine.

It removes harmful deposits and sludge and leaves engines clean, ready for new oil to circulate freely. It also helps free sticking valves and piston rings and should be considered a regular maintenance item.

Is Comma Engine Flush suitable for petrol and diesel engines?

Comma Engine Flush is suitable for both petrol and diesel engines. Where Petrol Engine Flush and Diesel Engine Flush were separate products, they have now been com- bined to make your choice easier— it simply makes sense to have one product that covers both engine types.


Is Diesel Magic/Diesel D-Tox suitable for vehicles fitted with a DPF?

When used as directed, Comma Diesel Magic or Diesel D-Tox is suitable for vehicles fitted with exhaust after- treatment units like catalytic converters and diesel particulate filters.

What about aerosol products for the workshop?

Comma have a number of aerosols in the range to help with various jobs around the workshop. Further details can be found online however the range has recently been revised and now includes improved formulations, less aggressive solvents in the formulations and new packaging to reduce waste.


Which of your greases are suitable for use in braking systems?

It is very important that the friction surfaces of any braking system do not have any grease on them at all. However it is common practice to use a grease on the back of brake pads and shoes to prevent squeal. The most suitable product that we have is Comma Copper Ease and this can be applied either by aerosol or with a brush from the container.


Where can I find more information on Comma ancillary products?

The information you require will be on our website with Technical Data Sheets and Material Safety Data Sheets (MSDS) available for free download.


Do you have application data for Comma ancillary products?

Where a vehicle manufacturer requires the use of a particular specification of grease (for example), it will be listed alongside all the other products from the Comma range that are suitable for it.

What coolant does & different types of coolant

What does it do?

Coolant protects against freezing by lowering the freezing point, it protects against overheating by raising the boiling point and it protects against cooling system corrosion, but only when it is mixed correctly with water.

All ethylene glycol based coolant achieves the rst two in a very similar way. It’s only when we start to consider the additive package, the bit that handles corrosion protection, that we start to see the differences between modern coolants.

Is there a “one size ts all” antifreeze & coolant?

Due to the huge number of applications and the increasing move to manufacturer specific coolant specifications, it is impossible to know which product is required for your
car without further details about the vehicle. This is being driven by changes in engine technology that are the result of increasingly demanding environmental legislation. New, modern engines require modern, high performance coolants. A single ‘industry standard’ ‘product will no longer suffice.




I notice you have a lot of different coolant products, what are the differences?

As far as the European passenger car market goes there are 3 types of modern antifreeze: a silicate technology based product (Xstream® G48), an OAT (Organic Additive Technology) based product (Xstream® G30) and a silicated OAT based product (Xstream® G40). For certain applications there is Xstream® G05 which would typically be used in heavy duty vehicles. When compared with the more conventional coolants, as well as lasting longer they also protect better and are designed to be more compatible with all the different metals, plastics and rubbers you nd in a modern cooling system. However, these high performance products use different additive technologies to protect the cooling system from corrosion. Different manufacturers have different requirements and to cover the vehicle parc we need 4 different antifreeze & coolant products. Coolant protects against freezing by lowering the freezing point, it protects against overheating by raising the boiling point and it protects against cooling system corrosion, but only when it is mixed correctly with water.

The Xstream® range of coolant products are also OEM (Original Equipment Manufacturer) approved and cover a wide range of specifications. Commodity products like our Super Coldmaster or Super Longlife Red have no such approvals and meet only the industry minimum standard of BS6580: 2010.


The coolant in my car is red, so do I just use another red coolant? 

It is always important that you check with the vehicle’s handbook or the Comma website that the right type of coolant is being used. The colour DOES NOT indicate that it’s the correct type, it is a dye added during the manufacturing of the coolant so you can visually see it (for example when checking the level in the expansion tank). A coloured coolant will also aid in identifying where a leak may be occurring.

What are the consequences of using the wrong product? 

Different manufacturers use different metals, plastics and rubbers in their cooling systems. When they specify a coolant for their vehicles they select the type of coolant that is more compatible and able to provide better protection. If the right type of product is not used a variety of problems like overheating and corrosion issues can occur. These can significantly affect the performance of your vehicle’s cooling system resulting in a variety of knock-on effects ranging from failed water pumps or broken radiator pipets seized engines. Increasingly, OEMs treat coolants as warranty critical part numbers nowadays and not using the recommended products can result in a void warranty claim.

How to get it right?

To make this increasingly complicated choice a lot easier you can use the Comma Application Guide or our website, where you can select your vehicle using the VRN (Vehicle Registration Number) too or by using the make and model search. You will then be presented with a printable full vehicle recommended product report including engine oil, antifreeze & coolant, transmission oils, break fluid and grease if applicable.

Can I mix different types of coolant?

Different types of coolant are based on different technologies that may not be compatible. Mixing different types of coolant could cause unpredictable results and potentially damage the cooling system. Like with any other car part, the advice here is to always follow the OEM’s specification.


How to select the right oil – Comma Technical Bulletin

The Right Oil for Your Vehicle

As with many areas of the automotive industry the world of engine oils continues to become increasingly more complicated with the appearance of more and more unique manufacturer specifications and a resulting shift away from commodity products towards manufacturer specific oils. This bulletin shows you how this can be made easier and also reduce the risk of potentially expensive damage to your vehicle.


Why is oil so important? 

Oil plays a vital role within an engine, as it performs three key functions: it reduces metal to metal friction (engine lubrication), provides a degree of cooling (engine cooling) and provides engine cleaning (with the use of detergents, dispersant and other additives). When the incorrect oil is used or the oil is not changed at the manufacturer’s recommended intervals or the amount of oil is not checked regularly between service intervals, it can lead to significant and costly engine damage.

Can using the wrong oil affect a warranty?

Yes. Engine oil is an integral part of the specification when manufacturers are designing engines. Engine testing carried out by the manufacturer identifies the right oil properties which are then converted into a code (specification). The right oil should always be used during the vehicle’s life cycle, however this becomes even more critical during the warranty period. Using the wrong oil can invalidate a warranty.

How do I select the correct oil for my vehicle?

The easiest way is to use one of our application tools. We would always recommend the use of our online application guide, where you can select your vehicle using the VRN (Vehicle Registration Number) or by using the make and model search. Our data is also available through various electronic cataloguing systems or you can also use the printed Comma Application Guide if you do not have access to any of these systems. All our recommendations are based on data provided by the manufacturers and come with a 100% compatibility guarantee which can be found on the website or the front of our printed application guide. Visit

Why is it important to determine the correct oil?

The time when a single grade of engine would cover almost the entire vehicle parc in now a thing of the past! Choosing the right engine oil has become more complicated due to engines becoming more complicated, fundamentally because of increasingly demanding environmental legislation. To meet the requirements, as well as changes in design and materials, vehicle manufacturers have to resort to things like EGR (Exhaust Gas Recirculation), exhaust after treatment systems and turbochargers to meet these demanding emissions regulations. The result is a shift towards OEM (Original Equipment Manufacturer) specific products. In conclusion, modern engines require manufacturer specific engines oils.

Oil Specifications Explained – Comma Technical Bulletin

What are specifications and why are they important?

Automotive engine oil specifications fall into four main categories: SAE (Society of Automotive Engineers), ACEA (European Automobile Manufacturers Association), API (American Petroleum Institute) and OEM (Original Equipment Manufacturer). Each has a different set of criteria that define the performance parameters of a particular oil and determine their suitability for use in various vehicles. When selecting engine oil it is important to remember that each set of specifications has a part to play in helping to choose the right product to help ensure the vehicle is operating as well as it can.


Viscosity Grade

The most prominent specification seen on any bottle of oil is the viscosity which is defined by the Society of Automotive Engineers or SAE. When it comes to choosing the right type of oil, viscosity is as important as any other speci cation and should never be ignored. Viscosity is a measure of how well a fluid will flow at a given temperature. The best way to describe this is by example. Water is a low viscosity fluid that flows freely at room temperature whereas treacle is a high viscosity fluid that flows very slowly at the same temperature. In practice, engine oil sits somewhere in between the two.


Industry Specifications

ACEA (European Automobile Constructors Manufacturers) have three sets of specifications which are referred to as sequences. The A/B sequence is the standard classification for petrol and diesel passenger vehicle and light commercial vehicle engine oils. The C sequence is a special classification for the same vehicles which defines low SAPS (Sulphated Ash, Phosphorus and Sulphur) or low ash oils that are required by some vehicles to protect DPFs (Diesel Particulate Filters) and CATs (catalytic converters). Finally, the E sequence covers heavy duty diesel applications.

API (American Petroleum Institute) have only two sets of specifications; the S sequence for spark ignition engines (petrol) and the C sequence for compression ignition engines (diesel). The S sequences for petrol engines generally apply to passenger vehicles and light commercial vehicles and the C sequences to heavy duty diesels. There are no classifications for diesel engines in passenger vehicles as this is not a big market in the US.

OEM Specifications

Almost every vehicle manufacturer has their own set of specifications for engine oil which may compliment or supersede both ACEA and API specifications. In recent years the number of unique manufacturer specifications has greatly increased resulting in a shift towards manufacturer specific oils. Increasingly demanding environmental regulations have led to much more complex and variable engine configurations which in turn can lead to quite different requirements for engine oil. This leads to different sets of specifications, even within the same make and model!


There’s more to oil than “C3” – Comma Technical Bulletin

There’s more to oil than “C3”

  • ACEA C3 should not be used as a ‘fit all’ product for vehicles with Exhaust After Treatment devices.
  • There are many types of Exhaust After Treatment friendly oils classified by ACEA ‘C’ sequences.
  • ACEA C3 doesn’t always match vehicle manufacturer specification.Charts showing how ACEA C3 performance levels compare to vehicle manufacturers specifications:

screen-shot-2016-11-01-at-10-38-40 screen-shot-2016-11-01-at-10-38-53

There’s more to oil than “C3”

It’s many years since viscosity alone, or viscosity and base oil type were enough to determine which oil was right for a given vehicle. It was once common-place for a single barrel of 10W-40 to be used for every vehicle that came in for service.

In recent years, the significant increase in vehicles fitted with exhaust after treatment units has resulted in many vehicles requiring so-called ‘low SAPS’ oils. Some technicians may be forgiven for thinking, or may have even been told, that replacing the old single barrel of 10W-40 with a new single barrel of low SAPS “C3” oil is a safe way to stock just one product that can be used in all vehicles. This could not be further from the truth – there is no single oil that can satisfy requirements for all modern vehicles!

Why can’t I just use a ACEA C3 oil in every vehicle?

Ultimately there are four factors which determine whether an oil is right for a vehicle:

  • The viscosity (SAE) – i.e. the oil’s ‘thickness’ over a given temperature range
  • The base oil type – i.e. whether its mineral, semi or fully synthetic
  • The oil industry speci cation – ACEA sequences such as ACEA C3 (or outside of Europe – API (the American Petroleum Institute)).
  • The vehicle manufacturer’s specification – e.g. VW 507 00

    Simply relying on the ‘oil industry code’ might satisfy one requirement of an engine but not the other factors.


Let’s take a look at 2012 VW Passat – a 2.0 TDI (130kW) fitted with an exhaust after treatment unit (Diesel Particulate Filter). You might think that by simply fitting a low SAPS “C3” oil will be safe, but as the diagram shows overleaf, a product that merely meets the requirements of ACEA C3 performs significantly differently versus one that also meets the requirements of the relevant Volkswagen specification.

What is Viscosity? – A Comma Technical Bulletin


The term viscosity means the thickness, or the ability to flow, of a liquid material at a given temperature – if you think about water and treacle at normal room temperature, then the treacle is more viscous than water. In reality, engine oil sits somewhere between these two. The higher the viscosity, the more difficult is it for the material to flow. However when a viscous fluid is heated, this enables the material to ow more easily. Viscosity is a very important factor when choosing the correct oil for a vehicle as it forms part of the OEM’s specification requirements.

Why are there two numbers for oil viscosity?

Most modern oils are described as multi-grade which means that they contain additives that improve their performance at
the extremes of temperature. The viscosity of a multigrade oil is shown as two numbers separated by a ‘W’ (or perhaps a dash or slash). Oils that only have a single number representing their viscosity are described as mono-grade and are usually only directly suitable for older, classic vehicles. These numbers DO NOT directly represent temperature, they are purely related to the viscosity of the oil (i.e. a 5W-30 viscosity oil does NOT mean it is only suitable for temperatures between 5 and 30°C!!!).


What’s the difference between a multi-grade and mono-grade oil?

Mono-grade oils are generally used for classic and older vehicles, when multi-grade oils were not available. For older vehicles, this meant that the oil needed to be changed for the winter and summer, so a higher viscosity when the climate was warmer and a lower one when it got colder.

This meant changing the oil on a more frequent basis, as a thicker oil would not perform as well as it could during the colder months. Multi-grade oils get round this by having a viscosity profile suitable for when the ambient conditions are cold, but also maintaining a suitable viscosity when warm and thus provide adequate protection all year round.

Is viscosity important when choosing an engine oil – didn’t you say before that it is dependent on the OEM specification?

When choosing an engine oil, it is important to observe the manufacturer’s specifications as well as the viscosity that they require. The viscosity is a fundamental aspect of the OEM’s specification, although at other times the OEM may allow for a range of viscosities. Always use the Comma Application Guide to ensure you get the right oil with the right specification with the right viscosity.

I see Comma now have more lower viscosity oils in the PMO range, why is this?

Most vehicle manufacturers are moving to lower viscosity oil (5W30s, 0W-30s, 5W-20s, 0W-20s) due to the fuel economy benefits that these bring. However, there are also targets and standards for vehicle emissions which must be met, and each manufacturer has their own way of achieving this. The different demands of the manufacturers has led to multiple products of the same viscosity and whilst we do our best to try and combine these specifications it’s virtually impossible to combine the requirements of every manufacturer into a single, cost effective product.

Comma recommends XT2000 15W-40 for my car on the Comma website but the dealer has told me I need a different viscosity?

The recommendations on our website are correct: they’re based on data from the OEM. OEMs can specify a number of viscosities for some models, and so it may be suitable to use 15W-40 or other viscosity. If you have any doubt then please contact Comma. Comma’s recommendations are 100% guaranteed.


How do I know which product to use on which car?

The safest way to make product recommendations is to use one of Comma’s application tools. At you will find product recommendations with 100% compatibility guarantee for engine oil and antifreeze & coolant for virtually every European vehicle going back over 30yrs, including system capacities and recommended service intervals. It also covers brake uid, gear oil and power steering uid should you nd you need some help with those as well.

Base Oil Types – COMMA Bulletin



The main component of any engine oil is base oil and all engine oils are classified as either mineral, semi-synthetic or fully synthetic depending on the type of base oil used (Figure 1).

Engine oils classified as mineral use base oils that are separated from crude oil
by conventional solvent re ning and are themselves de ned as ‘Mineral’. Engine oils classified as fully synthetic use so called ‘Synthetic’ base oils that are produced via a series of chemical reactions which tailor their properties to give a much higher level of base performance than mineral oils. An engine oil that is classified as semi synthetic is made from a blend of mineral and synthetic base oils in varying proportions and in performance terms fits somewhere between mineral and fully synthetic.

The American Petroleum Institute (API) has categorized base
oils into five categories. The first three groups are refined from petroleum crude oil. Group IV base oils are PAO (polyalphaolefin) oils. Group V is for all other base oils not included in Groups I through IV. Before all the additives are added to the mixture, engine oils begin as one or more of these five API groups.

screen-shot-2016-11-01-at-09-47-58How much base oil is used in the final product?

Typically base oil accounts for 60-90% of common passenger vehicle oil, with the rest being additives like viscosity improvers, detergents, dispersants etc. – which are tailored to different manufacturers engine requirements.

Mineral base oils (Group I & II). Where do they come from?

Mineral base oil is one of the products of crude oil processing, as shown in Figure 3. Unlike fuels (extracted directly from crude oil distillation), mineral base oils go through a series of complex, highly energy consuming and expensive refining processes. Different types of base oils are obtained depending on the chosen refining technique (Figure 4 shows the typical relationship between refining process used and resulting type of base oil)


I’ve heard Comma’s mineral and semi synthetic oils have gone from Group I to Group II. What are the bene ts of this change?

As we can see from the API Base Oil Categories (Figure 2), this change was driven with an increase in performance in mind. Oxidation and thermal stability are two key properties for engine oils and better performance at these levels means better protection against the formation of harmful acids, varnish, sludge and deposits that are formed at high temperatures. Other benefits from Group II when compared to Group I base oils include lower volatility which means there is less oil loss in high temperature operating conditions. Furthermore, the tendency is for new formulations that are being developed and tested by additive companies in conjunction with OEM’s, to use Group II base oils instead of Group I, which ultimately may create opportunities to expand the performance claims we make for the products affected by this change.

What products were affected by this change?

Only mineral and semi synthetic 10W40, 15W40 and 20W50 engine oil grades have seen the mineral base oil part of their formulation upgraded. This change doesn’t impact the range of applications but improves the underlying performance as previously described.

It is possible that users might notice a slight change in colour and smell of some of these products, however that is a consequence of this change, as colour and smell in this particular instance is not an indicator of quality or performance. You can be absolutely confident that you are actually getting an even higher quality product, backed up with Comma’s unique application 100% Compatibility Guarantee.


Gear Oils – How Do They Work?

Why the correct application is so important to the vehicles health.

While everyone recognises that it’s important to identify and fit the correct engine oils by application, it’s no less critical to follow the same practice with gear and transmission oils. Using the wrong engine oil can damage sensitive components – notably turbos, CATs and DPFs. It will also compromise engine life and performance, impair fuel economy and – if it doesn’t comply with the VM’s specifications – could easily invalidate the vehicle’s warranty.

If the wrong gear or transmission oil is fitted however, the vehicle is unlikely to move very far before some sort of problem arises: it might not even make it out of the workshop. While the wrong engine oil may take its time to punish, the wrong gear or transmission oil has a much shorter fuse.

In some ways, gear oils have an easier time than engine oils since, in the main, they don’t come into contact with the by-products of combustion such as gases, acids and other pollutants. Nevertheless, they have to operate in a different but equally demanding environment where metal surfaces are doing their utmost to come together and, if unlubricated, destroy one another.

Because oil pressure can’t always sustain an oil film between these surfaces and keep them apart, extreme pressure (EP) additives are used which are designed to literally ‘sacrifice’ themselves by creating a coating on the gears to increase protection. This is especially important in differentials where the torque loadings on spiral, hypoid gears simulate even more of a ‘grinding’ effect than straight cut gears.

What’s the difference between engine and gear oils?

Whereas engine oils have US specifications issued by the API (American Petroleum Institute) and European limits set by ACEA, the major standard for gear oils such as GL-4 and GL-5 are solely set by the API, though they’re employed worldwide. Gear oils adopt a similar viscosity classification system to engine oils, although the SAE numbers for gear oils don’t exactly equate to engine oils.

Although there are a large number of possible bands to describe the viscosity of manual gear oils, modern 75W90, 75W80, EP75W80 and 75W products account for over 50% of current applications and, between them, embrace nearly all GL-4 and GL-5 Service Classifications (75W products, such as new Comma MVMTF Plus 75W, are increasingly being specified to operate over a wider range of temperatures and provide additional ‘feel’ for contemporary high performance gearboxes).

Product Ps

GL-4 is generally preferred for gearboxes, since it prov ides the correct mix of protection for components against wear and the necessary degree of friction for the most efficient synchromesh operation. GL-5 prov ides the additional protection required by the final drive where the loadings tend to be higher.

When it comes to automatic gearboxes, power steering pumps and torque converters, the market is dominated by two fluid types, designated Mercon and Dexron. These have evolved over many years to suit the auto gearbox designs of Ford (Mercon) and General Motors (Dexron), but they ’re also widely applicable to some proprietary and ‘derived’ units such as Borg Warner, Rolls Royce, Jaguar etc.

As always, the devil is in the detail and a word of caution is in order. As with engine oils, there is no such thing as a ‘one size fits all’ solution in the gear and transmission lubes sector; the market requirement is too diverse.

For this reason, upgraded and new products for the widest number of applications are routinely introduced to Comma’s gear and transmission lubes offer to workshops, thereby reducing the reliance on sourcing the correct, OE-compliant product from a main dealer. A recent case in point is one new product and three important upgrades extending Comma’s coverage to 84% of UK car parc manual transmissions.