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I am going to change the transmission oil in my 6 speed 2001 S Boxster. I am dealing with the infamous 1st - 2nd gear when cold shifting problem. I am thinking about using Mobil 1 LS 75W-90. Has anybody used this lube before, or know if this is appropriate? This is a synthetic GL-5 lube.

:renntech:

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I am going to change the transmission oil in my 6 speed 2001 S Boxster. I am dealing with the infamous 1st - 2nd gear when cold shifting problem. I am thinking about using Mobil 1 LS 75W-90. Has anybody used this lube before, or know if this is appropriate? This is a synthetic GL-5 lube.

:renntech:

A copy of my response to the same question on another site:

I would not use Mobil 1 for a very simple reason: I emailed their tech line and was told that “Mobil 1 does not have appropriate gear oil for your application.”

I would agree that changing the gear lube more frequently than the factory call for, but Porsche has gone to lengths (as with other components) to prevent the after market from replicating the correct formulation (they use obtuse specs that no one in the US, who use API specs, seems to be able to discern).

As for those who have gone in a different direction, we have a 2004 Japanese car in the shop at the moment that the owner used a Mobil 1 product in his 6 speed, and for nearly a year had no issues (actually felt the shifting was improved); then suffered severe shifting issues that we traced to disintegration of the synchronizers. We queried Mobil 1 and got the same response, no appropriate product for the application (in this case the correct spec was for a GL-4 rated lube, which Mobil does not have).

I have seen several postings on this site, and others, that offer conflicting and usually unsubstantiated opinions on which gear oil is safe/correct/better in Porsche gear boxes; often contradicting other postings. Contacting the manufacturers of gear oils has also proven disconcerting as some appear to have said yes and then no to the same question at different times.

That said, the factory fill is a full synthetic, and is readily available from dealers willing to discount it somewhat (e.g.: Sunset), it seems a conservative move to use what the factory likes, even if it cost a bit more. As these gear boxes use less than three quarts of lube, and a new gear box costs a ton of cash, using Porsche’s over priced lube would seem a reasonable pathway………….but that is just my opinion…………….. ;-)

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