[JFP in PA]

Originally Posted by cnavarro

I would file that response under the cookie cutter answer. If I ask my Mobil rep, they wouldn't know what a Porsche was :-) - just a bit of an exaggeration, but you get the point.


Since the gearbox is sourced from VW/Audi, it would take the same fill and their lube may be a fully-synthetic GL-4 rated gear oil. There are VERY few true GL-4 oils available, most out there are GL-5 rated (which is supposed to be backwards compatible).

The tip's differential on the other hand calls out specifically for a GL-5.

Technically, any 75w90 or 90WT GL5-rated gear lube should meet the requirements for the gearbox IMHO.

It's best to google about vw/audi gearboxes rather than Porsche ones, since you'll find a lot more information and discussions about the vw/audi counterparts to the Porsche ones.

I have less respect for Mobil 1 everyday............

Just for informational purposes, Red Line continues to offer a good selection of GL-4 full synthetic gear oils. Reason I know this is that Nissan continues to require GL-4 gear lubes and the syncros (and some bearings) they use don't seem to last very long with GL-5 oils. We've used the Red Line GL-4's in our client's Nissans with great results.

For what it is worth, under the API specs, the additives’ that make a gear oil a GL-5 should make the oil incompatible with a GL-4 gear box. I know some oil companies have claimed to have oils that can be used in either one, but having seen what a GL-5 oil does to the internals of a GL-4 Nissan gear box, I really wouldn’t trust the claim that a GL-5 is always backwards compatible………….