AudiWorld Forums - The great oil experiment (or is he f-ing crazy?)

So, how many of you would put $2.98/Qt (including tax) Group II+ Dino oil into their $70K RS4?

For the past month and a half, on the recommendation of Terry Dyson, I've been running Shell Rotella T CJ4 10w30 oil in my engine. This is a heavy duty diesel truck oil. We went down this path based on his knowledge of oils and his theories about the fuel dilution problem being due to inadequate ring seal, and wash down due to direct injection.

As many of you know, we've been looking at various "approved" oils in this engine, along with several other owners, and have come to the conclusion that there is no Audi 502 oil that we can find that performs well in this engine. Terry did some research, and came up with two non-502 possibilities. This is the first one, which we now have 1600 miles of test data, that can be compared to the oil analysis record. (BTW, for those that are interested, we now have 25 oil analysis samples taken on 8 different RS4s scattered across the country.)

When I changed to Rotella T I was very keen to listen to the engine and note any differences. It would figure that the 1st week the oil was in my engine temperatures in New England dropped below 10F. Start up was fast and normal. No different than Motul, which is not surprising, since Rotella T has a pour point of -40F.

Anecdotally, I noticed two differences as I drove. First, the engine seemed to have a deeper growl than I'd remembered. Could have been my mind (or ears) playing tricks on me, but the engine sounded stronger. Second, oil temperature dropped through the floor. I posted a question about this a few weeks back, and my memory was correct. My oil temperature is generally running 5 to 10 degrees lower than I've ever seen it over the past 15,000 miles.

Well, an oil analysis just came back and the results are amazing. Fuel dilution is down to 1%, the lowest this engine has seen. Flashpoint is up to 340 F, the highest in our sample record. All wear metals are down by 25% or better. And the analysis results confirm better ring seal than has ever been seen in this engine, by a nearly a 2:1 margin.

So, oil does make a difference.

At this point, we've found an oil that works well in this engine, although it is not an extended interval oil. Heck for less than $3/Qt, who cares?

However, not to be content I and several other owners are going forward with the next step in our great experiment. I've worked with Terry to have a specially formulated racing oil designed specifically for this engine from a small high performance bio-degradable oil supplier. The oils these guys make is supposed to be nothing short of amazing. Three of us have ordered it, and two of us will be changing to it tomorrow. We'll keep y'all posted with the results as they come in.