Mr.88-80Q

I've got an 88 80Q with about 230,000 miles. I havent changed the rear diff oil since I've owned it from a 124,000 miles and want to do it soon. Any you guys have any advice on oil for that car. Stealer is trying to get somethin like $80 for the oil alone. He told me the new synthetic oil doesnt absorb moisture. Does that include the entire quattro range or certain models? I have a vacuum pump but also need to get that 17mm adapter. any ideas will be helpful...

absolutcq20v

One thing that can screw you: loosen the top (fill) plug before the bottom. If you get the bottom loose and drain the oil and the top on is frozen solid...no way to get oil back in.
I bought a 17mm socket online for something like $4-5 bucks. It arrived to me via mail in 2 days and is of solid quality. Good luck.
I did my diff oil awhile back and don't recall the oil at this hour, but many others here can help you out.

squidix9

Do a search here for "synthetic oil", and you'll find pages of useful information.

I run NEO Synthetic Oils exclusively in my car, and they're great. You should find a brand you are comfortable with though.

I run NEO 75-90 in the rear and RHD in the tranny.

Be careful with your GL: ratings though. Never use GL5 where there is any yellow metal. The extra HP additives will oxidize the brass, and may cause catasophic failure.

Some synthetics are rated GL5, but are safe for yellow metals, check with the manufacturer first.<ul><li><a href="http://www.neosyntheticoil.com/index.html">NEO</a></li></ul>

mityVR6

Motul Gear 300 is a fully synthetic gear oil rated to GL-4 and GL-5 specs.
-Adam