Hi Gary,

I have upgraded to synthetics whenever I can find them. Don't forget the crush washers first. Mine took 17mm id for drain and fill plugs. See summary document below:

Synthetic Fluids Plus:

Mobil 1 synthetics are good for: Automatic Transmission (Use the same "ATF" for power steering.), Rear End (Use the same "75w-90" weight gear oil for Timing Belt Tensioner.). Mobil 1 has a good rep, and is less expensive than most - $5-6/qt. Castrol Synthetic Blend motor oil is good. The blend is about half the price of the 100% synthetic - $2.6/qt. I have heard that you can change oil less frequently with synthetics. Distilled water and aluminum safe antifreeze - like Prestone (non synthetic) work for Radiators, but NOT the new Prestone in older cars. (Check the archives for other antifreeze recommendations, if you want something more exotic.) Use Valvoline synthetic Wheel Bearing grease. Use ATE Super Blue Racing brake fluid, alternate flushes with Gold. It is German with a high boiling point.

Replace caliper and master cylinder bleeder valves with check valve type for easier bleeding. Crush washers for the differential fill and drain plugs were 17mm id.

Thom Ross


Differential fluid.

See http://members.rennlist.com/pirtle/svc.html. I used Valvoline 75W-90 and car is smoother/better (no more shudder when accelerating in a turn). The old stuff drained like coffee with cream mixed with chocolate milk.... I would also recommend getting the $2-3 hose which fits to the oil bottle - it will make the job cleaner and you less stinky. :)

John Pirtle


At 01:19 AM 6/9/2003, BrianG wrote:
>Having just finished the timing-belt project, including the tensioner re-build, I just read that I should have used regular engine oil for the tensioner. As per the usual sources, I did the tensioner re-build with heavy-weight oil recommended. Should a guy purge the tensioner with regular oil?

I doubt that it makes much difference, especially in the later cars with the fill/bleed nipples. It didn't seem to be important enough for Porsche to change the Factory Workshop Manuals, even though they issued a Tech Bulletin recommending engine oil for the later cars.

It perhaps isn't common knowledge that there isn't as much difference in the viscosities of gear oil and engine oil as the numbers would suggest. The SAE viscosity numbering system adds 40 to the viscosity of gear oil to help distinguish it from engine oil. In other words, SAE 80 gear oil is the same viscosity as SAE 40 engine oil.

The additive packages don't make a lot of difference in this particular application. The gear oils have EP (Extreme Pressure) wear additives, the engine oils have other additives to make it suitable for engine use.

Wally Plumley
928 Specialists