I use Mobil 1 in my S8 all year.

what the real diffs are? i mean, i effectively have just a slightly less high temp capability with 0w-40 than 15w-50, right?

Start from the beginning.

If you are serious about racing we are talking some real preparation.
1.All synthetic in all of the drivetrain.
2.You have the best gas and a serious octane booster.
3.Engine gets fresh synthetic EACH time you take it to the races. You check the diffs for fluid drop or change in smell each time. Send motor oil and torsen dif fluid to a testing company after the first race!!!
4. You have a vag-com to watch and log what is happening.

This is what I'd advise for a start. Long before you get some good tires.

Drag is really hard on the drivetrain, but not as hard on the engine as tracking. As long as you use good quality synthetics and use the testing to assess what is happening to them you will be fine. Vag-com or peak hold guages will really help in dialing the car in...safely.

PS I wouldn't run above a 10w30 syn.

15w50 is fine for an old school wide-tolerance street "racing" V-8. They are way undercooled to begin with. The superheavy weights are leftover from the beginning of automobiles. Even Nascar and the dirt trackers use "light-weight" synthetic oils.

I have a GM manual here for a vortec 350 that specifies 5w30 synthetic with a 0w30 winter advisory. It goes so far as to state that ANY 20w50 is specifically detrimental to the motor. How is that for a US car company!? Audi uses very similar recommendations.

Quote me: You don't use oil or spark plugs to make up for bad design! You fix the problem and use the correct part.

...regardless of their weight. For that reason, I'm sticking with 0w40 until I find a reason to change.

Audi engines in the past have run 20/50....
My family who has owned numerous Audis over the years, from 83, have clocked over 200,000 miles on many of them have run 15/50. Engines still ran fantastic when they were sold...
The shop I used to work for in Dallas specializing in Audi and VW used 15/50 Castrol as well.

You CAN run whatever YOU choose. Audi since the mid-ninety's has been specing 5w. RTFM? And, every Audi dealer I have met runs whatever is in the 55 gal. drum regardless of the climate.

You have provided a tribute to Audi engines, not a rebuttal with any facts.

<center><img src="http://pictureposter.audiworld.com/475/getimage.jpg"></center><p>Maybe you dont live where you see 100 degree weather for almost 3-4 months straight....
Pulled straight from the Bentley...

factory electronic shop manual, email to me from a friend in a UK Audi dealership.

0W-40 is the ONLY recommended oil for Audi's HIGHEST performing cars. In 100 degree-plus weather.

Using anything else is the dealer's way of increasing their profit margin. AoA doesn't spec it so dealers aren't painted into a corner and have to use it.

It's called progress! LOL

<img src="http://www.audizine.com/uploads/imagepath.asp?id=677&A=p">

If you live in northern latitudes where the temperatures rarely get into the 80's or 90's F, you do not need more than a 0W-30.

If you live in the hot southern latitudes or desert climates, you may run a 0W-30 in winter, but you will need a 20W-50 in the summer for the 100+ F temps you will encounter.

This is especially true if you run your oil to the limits of its viscosity. Even sythetic oils begin to break down after several thousand miles. Just watch how well new oil adheres to your dip stick and then watch how poorly oil with 7500 miles adheres to the dip stick. The difference indicates viscosity breakdown. I feel certain that my summer 20W-50 protects about the same as a 10W-30 by the time my winter oil change becomes due.

You are fortunate to NOT have a 3K turbo with limited bearing surface area. 20W-based multi-viscosity is too thick for effective lubrication at cold start-up in the 2.7L turboed engines.

Which is fine I suppose if you never see that temperature. about 5 months out of the year I see that temperature and above...

heheh

The chart clearly describes 5w30 as being appropriate for all temperatures (left open column). I miss your point.

BTW. Bentley is not Audi any more than Haynes is.

The only places I can find it are Mercedes and Porsche dealerships. At mega$$/quart. I called Mobil 1 to ask why it is not more widely available, and they said because it is not manufactured in the US.

I would love to find a source here other than the two I mentioned above...

TIA!
Paul

i found it at the first napa place i called, but didn't want to drive out there. so i called a distributor of mobil 1 products (found from their website) and gave them a ring. If i were you, id do a lookup on their site for a distributor near you, and give them a call. i had no trouble getting 6 qts for like 27$. I used commercial-ulman, no trouble at all. but there were many, and i doubt you're in Cleveland (where they are located) though i bet they'd ship....

...that's who the local Mercedes & Porsche dealerships get it from.

<a href="http://shop.store.yahoo.com/parkplacemotorcars/mob1trismoto.html">Mail-Order Mercedes Dealer</a>