Engine, Transmission, and
Differential Lubricants


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Maintenace & Consumables

Engine, Tranny, & Diff. Lubricants

Engine Oil


Tranmission & Differential Fluids


Engine Oil
Everybody's got their favorite brand of oil, so I won't even try to tell you what to use. I also won't get into the synthetic vs. dino debate. The most important thing is that you change the oil and filter regularly. System capacity is 5 quarts.

The drain plug is 26mm x 1.5 thread, and the washer is 26mm ID x 31mm OD x 2mm thick. I had trouble getting the correct size from parts places, so I bought an oil drain valve. It makes this job much cleaner and easier. Thanks to Chi Wong, I now have the source for these valves. Go to http://www.fumotovalve.com for information and ordering. The 20V engine uses P/N T207.

If you'd like to replace the stock plug, proper plugs are available from C.G. Enterprises (see #1042 or #1043). They also can supply the crush washers (#2058).

I don't want to get into the filter debate either, so let me just say that I use the OEM Mahle brand. For a good comparison of oil filters check out this oil filter study and german oil filter study. The original P/N for our cars (Audi 056 115 561 G, Mahle OC-47) has been discontinued. The replacement (Audi 034 115 561 A, Mahle OC-154) is the same filter that is specced for the turbo cars, so it's probably a little better. They're not too expensive (~$3.00 ea.) if you buy a case of 10 mail order from German Parts and Restorations (800-321-5432), Halsey Imports (800-792-0081), or Impex (800-736-3550), to name a few. There are other good brands out there, so take your pick. Just make sure that they have the anti-drainback valve and the bypass valve.

Transmission & Differential Fluids
The owner's manual states that the transmission and differential fluids never need to be replaced. However, many owners (myself included) report good results from replacing them with fluids from Redline, but I'm sure there are other suitable brands. Smoother shifting, (hopefully) longer life, and even slightly better gas mileage are the rewards.

Transmission/Front Differential
Synthetic GL-4 75W/90 oil is shared by the transmission, front diff., and the TORSEN center diff. Redline MT90 is the replacement of choice. The system has a three quart capacity. DO NOT use GL-5 oil in the tranny!!! This includes products from Mobil-1 and Castrol (Syntec), since as far as I can tell, they don't offer a GL-4 variety.

Rear Differential
The rear differential takes 0.8 quart of synthetic GL-5 hypoid oil, which corresponds to Redline's 75W90. Low fluid and oil presence on the side of the differential case can be a sign of bad seals.


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