mark kibort

again... most oils are fine for street use, and synthetics are good for holding up for longer change intervals, but my concern is more about the dirty oil not the condition of the oil suspending the dirt .......... so, you will be fine with most oils ..... but, if you plan to track it, or live in hot conditions, I wouldn't touch the oils that have proven to break down at high engine temps.

Petza914

In my 928MS Supercharged 928, Carl has recommended using Shell Rotella 15W-40 petroleum based oil, which is a Turbo Diesel oil. He says the seals in these older cars need the petroleum to avoid shrinking and maintaining a good seal, otherwise, you're prone to get oil leaks. He says is you must use a synthetic, use a blend so the seals stay happy.

http://www.shell.com/rotella/products/tpl-pro.html

hacker-pschorr

Here I thought this was going to be just another boring oil thread.....

mark kibort

I think that is too thin when hot..... also, i have had no leaks or seal issues with running pure synthetic over the past 15 years and over 5-6 928s of mine or friends ive been racing with.
Im curios why a 40weight would be recommended when all of us seem to agree that the 20-50 spec should be followed.

AO

Yeah... I tried that stuff back in 2007. Even started a thread about it... don't think I closed it out. Short story goes like this. Cool days, no problem. One hot day... lost oil pressure. Warning lights came on. Drained it that day and went back to M1 (15w-50).

As for blends... snake oil. Just go full synthetic.

Carl Fausett

Pete's car is a 16v street car. It will likely never see a race track.
Go to the 20w 50 if that makes you happy.

Just select oils that still contain ZDDP in the right quantities. The Rotella T is good, and cheap.

...and 50/50 synthetic blends are not snake oil. See Brad Penn. But that's a whole 'nuther page....

mark kibort

I just thought in general, its better to run the spec 20-50, even for street use.

Carl Fausett

I have had excellent success with the 20W-50 Rotella T also.

Petza914

Carl, I see a Formula Shell 20W-50 but not a Rotella version in that weight, just the 15W-40. Is that what you're referring to with the 20W-50?

19psi

I've been using T6 in my motorcycles (including two turbocharged) for many years.

5W-40 is all that I can find in my area. Where are you buying the 20W-50?

Carl Fausett

No, Rotella T comes in a 20w-50. It just might not be summer-enough for them to put it out on the shelf. The difference between it and the 15-40 is no worry for your application. The 15w-40 would be fine.

That said, read up on the Formula Shell version, (I havent) it might also be a good choice.

RedPanda

Wait, there is a season to put heavier weight oils on the shelf?!