VoilaGT3

Hi all,
been doing a solid bit of reading on it and looking to see what current preferred lubes are for the diffs. I also read some crazy left field debates over viscosities and such, so clarity would be appreciated as well.
TIA!

phatz

anything thats meets spec ...its irrelevant

Petza914

I use Driven LS 75/90

JAGMAN1

I’ve used everything from the porsche fluid to Redline 75-90, to Liqui moly 75-90. Each of the major manufacturers make a fluid that will work well in the Cayenne. Go to the Redline website, or to FCP’s website and you’ll find what’s listed for your CTTS.

hahnmgh63

I'm also a Redline believer for gear oil. They do make thicker fluid which may or may not be a better route to go, especially on the front axle with all of the premature failures although I am using 75w/90 Front/Rear. I'm not in a believer that the manufacturer knows best in many cases otherwise there wouldn't be so many front axle failures, plastic coolant pipe failures (that Porsche completely denied for the first few years until it became an epidemic), 4.5S (and even some Turbos) bore scoring (remember when the 955 first came out Porsche recommended a 20k Service interval, after about 2yrs they shortened it to 10k but that is still too long, and they as well as other companies are still recommending Mobil 1 even though pretty much every oil sample test you see online using Mobil 1 shows that it is completely done by 6~7k miles. Mobile pays these companies millions of dollars to use their name for adverstising. Yes it will get you out of warranty and probably to 100k but not much longer, unless you get bore scoring due to bad engineering (4.5S has Cast pistons and tight cylinder tolerances, Turbo are Forged pistons but still tight) and long Mx intervals (some poor oil choices). Original 955 fill for the gear oil was a Dino Oil, I'll have to look at the Spec sheet now but I think Porsche changed it to a Synthetic oil (doesn't help those that ran that Dino oil for years).

19psi

Turbos being immune or less prone to scoring is a MYTH created by wrinkled pants.
I've read of far more CTTs on this forum with cylinder scoring vs normally aspirated. A quick Google search will show the same on renntech and 6speedonline.
Now factor in that fewer turbos were manufactured.
The 2008 Turbo is the biggest POS out of all years and models when it comes to scoring.

My '04 (built in '03) wants an oil change every 4,000 miles, and starts pestering me at 3,000 miles during startup. It's old enough that I can reset the warning by using the trip reset button.

VoilaGT3

Thank you guys for the brand drops, I trust those for sure. Anyone know wether 4, 4+, or 5 is a good idea? I read they are not good for parts with certain kind of metals in them.

theprf

The warnings about metal compatibility are for manual transmissions using brass syncros, so they don't matter for the diffs.

hahnmgh63

If you're asking about the GL rating, you definitely want a GL-5 for the axles, GL-4's are for manual transmissions as they don't have the sulphur Extreme shock additives which can be detrimental to Brass Synchros.
I have seen many more normally aspirated 4.5's on here with bore scoring than Turbos. I'm talking about bore scoring not necessarily Oil usage as the Turbos will always use more oil but not necessarily due to bore scoring, usually due to the crankcase ventilation from higher cylinder pressures and blowby, and in later years and higher mileage as much due to worn Turbos as Valve guides or Rings. Now if you know of Jake Raby at Raby Aircooled Technology and Flat Six Innovations (Also tightly linked to LN Engineering)(The real brainchild behind real 996 motor fixes). He builds custom Cayenne motors too and has seen many more normally aspirated than Turbos. There cylinder clearances are very similar but the Normally aspirated use Cast pistons which expand more than the Turbo's Forged pistons which tends to cause more metal to metal contact.
https://rennlist.com/forums/cayenne-...ll-scored.html

VoilaGT3

spot on, my reading was less than to the point with a lotof tech-dribble.

hahnmgh63

Yea, the GL-5 (and unofficial GL-6) ratings for Extreme Pressure are for Gear meshing and extra bearing protection and definitely what you want in our front and rear axles. Any of the top Synthetic (Redline, Liquimoly, Lubrimolly, Amsoil, Driven) will extend the life of any of your gear components but they can't repair previous damage. Even most of the big companies (Shell, Valvoline, Mobil) full synthetic gear oils are still better than the original fills were back in the mid 2000's. The Porsche gear oil spec is SAF-AG4, it was developed by Castrol and was a high standard but pretty much all Synthetics nowadays exceed the AF4 spec.