mitch48

I bought a 2012 Cayenne base a couple of weeks ago, and I'm going to flush the diff oil, transmission oil(automatic) and the coolant. Brakes were done just before I bought it. What are recommended fluids for all three of these systems? I think I can use phosphate free coolant, just as I do in the Cayman, but the diff oil is a mystery and the tranny I think can use other oils besides the Porsche branded stuff.

Dan87951

I don't know specifically about your Cayenne but when I spoke to a Mobil rep he told me I could use 75W90 LS in the diffs on my 955 series CTT. He said to make sure the bottle has "LS" as it contains the slips additives that are needed for the 955 series differentials. Can't remember how many quarts I bought of Mobil 75w90LS but have about 9k miles on it and so far so good. I do have a youtube video on changing the diff for a 955 series Cayenne. It may be of help to you? Changing the differential fluid on my Cayenne was easier than an oil change. Pretty straight forward stuff.

mitch48

Yeah, from all I can see, the diff fluid change is pretty straightforward, just open the drain plug, let it drain, replace plug, pump new oil in the fill plug until it starts coming out and secure the plug. Same for front and rear diffs. I also plan to change the auto trans fluid and filter, a little more involved, and like my automatic BMW's the fluid has to come up to the proper temp to get an accurate reading on "full." I've got several bottles of Mobil 1 synthetic gear oil, may just use that.

Dan87951

Yep that's pretty much it. Make sure you crack the fill plug loose first before the drain plug.

mitch48

Yes, that's the first rule, make sure the fill plug will come loose before draining the oil out, else you're stuck.

hahnmgh63

Don't use the 75w-90LS unless you have the rear Limited slip option 1Y1. Otherwise just use a top quality Synthetic GL5 gear oil in the two diffs.

Dan87951

Mobil 75W90LS fluid is backwards compatible with open and limited slip diffs.

hahnmgh63

That may be true but I would prefer not to use an oil with a Friction Modifier in a open differential if I had the choice.

Dan87951

It's not a "may be" it is true all you have to do is read the back of the bottle. I'm pretty sure Mobil's petroleum engineers know what they're doing. After all they have been in business for a very long time.

OP, the key is to change it often and not to get wrapped up on hyped up brands/magic oils.

Dude174

I just did this 2 weeks ago. Used Mobil 1 for diffs, ordered transfer case fluid from pelican parts - Fuchs I believe is brand. It was all pretty easy, front diff had like a cup or 2 of fluid in it! All fluids were black and very dirty. Much smoother and quieter afterwards!