Factory recommendation is every 48k miles.

I use Castrol XJ 75W140 in my 30k miles-old 951 tranny and it feels much better than the factory 75W90 oil it had been fed with.

 

Update to this thread. I switched from swepco to Red Line 75W90NS from Jason at Paragon's recommendations. Unfortunately Paragon was out of stock so I got it from here: http://www.synlubes.com/ they are in the same state as me so I got it next day. In the end the difference is AMAZING! My trans shift so much more smoothly then it did before. I have NO differential noise and second gear goes in like a dream. Now, this is my NON-LSD trans. So if you have a NON-LSD trans and swepco, call up Paragon and get some Red Line 75W90NS.

 

not sure if this thread is still alive but i'm about to put in some 80w-90 amsoil fluid in my turbo s with the limited slip, the amsoil just seems really thin compared to non synthetic but i guess you guys are having good results with the amsoil..

if anyone has any sugestions let me know

 

I used Redline 75/90 NS buy mistake in my LSD tranny, shifted great, had some chatter from the diff though. I just put amsoil 75/90 sever gear lube in my Subaru and I like that too.

 

I change my Amsoil every 2 years or 20K miles

 

----- "I guess at 94k miles I should change mine, huh? Probably never been done."

uggghhhh

every three oil changes. for me that's @ 20k miles. If racing, every 2, 3 events even isn't unreasonable.

I am amazed to hear such a variance of opinion about lubricants. I believe that it's far-too-infrequent oil changes over the car's lifetime that's at the root of all the fuss.

 

I'm using Royal Purple and no problems at all. Actually I'm runing it in three different cars since it complies with GL4 and GL5 requirements. Porsche dealer actually told me to use GL5.