CAT’s Inside Line: Comma


1.       Engine Oil

a.       From 2008 onwards, Audi A4s rolling off the production line were starting to operate on extended service intervals by default which meant that the only engine oil that you could use has to meet Audi’s highest specification. Regardless of service interval, diesel models were routinely fitted with expensive exhaust after-treatment units such as DPFs which again means that only the highest specification, low SAPS oil could be used – Comma Prolife 5W30 from our range.  In some cases there are more cost effective alternatives for petrol vehicles that have been switched to operating on a fixed service interval but you should always check our application guide at to ensure you get the right product for your vehicle every time.

b.      The very long service intervals operated by Audi for this period make oil top up between services even more critical. Operating a vehicle for any length of time on too low an oil volume will can have catastrophic consequences particularly for sensitive components like turbo chargers. Supplying the customer with a top up pack and reminding them that they should be checking the engine oil regular (see handbook for guidance) might also be prudent here particularly if you have noticed that the oil needed topping up when it was brought in. The vehicle may not return for a service for up to 2yrs!! A quick check before you change might be a good way of reinforcing the importance of top up to the customer.

c.       The Pumpe Duse, or unit injector diesel engine was still used in some Audi A4s up until around 2009 when VAG went back to a more conventional common rail design. The design of the PD engine means that extra stress is placed on the cam which is used to drive the fuel injection pumps – one per cylinder. The use of the wrong specification of oil, particular in engines of this type running on long service intervals can cause excessive wear on the cam lobes used to operate the injectors which is very costly to repair. Always use to identify the right product for your vehicle every time.

2.       Brake Fluid

a.       For almost all variants of the A4 from 2008 onwards, Audi specify a low viscosity brake fluid to ensure that the electronically controlled braking systems such as ABS and ESP work effectively in all conditions. This equates to Comma DOT 4 ESP from our range. Always use to identify the right product for your vehicle every time.

b.      Most people don’t think of brake fluid as a service item however, as with many manufacturer’s, Audi specify a change interval of 24months for this series of the A4. Brake fluid degrades over time by absorbing water from the atmosphere (even when it is apparently sealed inside the system) which lowers its boiling point. Boiling point is a critical factor in brake fluid performance because of the amount of heat generated during braking. If the boiling point of the fluid is too low then continuous or hard braking may cause the brake fluid to vapourise which in turn can result in a loss of hydraulic pressure within the system (ie your brakes don’t work when you most need them too). The message here is that brake fluid is a safety critical item so check and change when specified – don’t assume that it will just be OK.

3.       Power Steering

a.       For this series of Audi A4 there should just be a single specification for power steering fluid which is covered by Comma CHF11S however you should always verify this using Comma’s application guide available at just to be on the safe side.

4.       Coolant

a.       Audi are very specific when it comes to coolant and for this series of the A4 there is currently only one product that you should be using. Xstream G40 is based on BASFs Glysantin G40 which was developed specifically for VAG and is the approved technology for all of their vehicles, including the Audi A4, from 2008 onwards. That said, we are starting to see a new product start to appear in the very newest VAG vehicles rolling off the production line so it is still prudent to check the requirements of the vehicle you are servicing at just be on the safe side.

5.       Transmission

a.       VAG vehicles like the Audi A4 use a wide range of transmissions which attract a huge number of different specifications. If you are servicing the transmission it is critical that an application guide is used to get the correct product. Comma’s application guide is available on our website –

b.      A popular type of transmission for VAG group vehicles is the DCT or double clutch transmission. It is important to note that there are two types of DCT used by VAG which operate on two different fluids. You therefore can’t assume that because the transmission is described as a DCT that it operates on the same, specialist DCT fluid. Use Comma’s online application guide available to identify the right product for your vehicle before beginning a service.

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