There's been a fair amount of discussion about oil in our engine (moreso from the RS4 folks). Based on that, and since I'd like to avoid any serious problems with the timing chain & other related bits, I figured it might be worth it to step up from a better oil.

Since there's not a good collection of oil data for the S4, I figured I'd have a few samples taken over the next 10-15k miles.

The test data showed a fairly high level of fuel dilution. Based on the data, I've decided to do an early spark plug & air filter change.

I'd like to encourage a few S4 owners to do a few tests as well so we could build up a better database. Terry (of Dyson Analysis) is sharing the S4/RS4 data he gets with an RS4 owner (Scott) who's been collating all of the S4/RS4 data.

http://www.dysonanalysis.com/<ul><li><a href="http://www.smoe.org/jeffw/audi/s4_oil/1255001_Jeff%20Wasilko%20Wakefield,%20MA_2006%20S4 _07110752.pdf">S4 oil analyis</a></li></ul>

of the state of tuning. Thanx Jeff.

I would think it would just require more frequent oil changes and possibly a better grade of oil as a remedy?
Are you thinking oil is getting into the combution chamber and fouling the plugs?
Isn't fuel dilution caused by fuel getting past the rings into the oil, not the other way around?
thanks in advance

I'd cut the oil intervals down shorter. 280F flashpoint is ridiculously low.

I don't think your wear metals look bad at all, esp since you used Mobil 1 0w40 which is known to contain a fairly high level of metals in its virgin state.

Dave

it seems that the fuel dilution and flashpoint are related....

From the 12.3 vis@100C, you can tell that it sheared quite a bit, which would also lead to the low flashpoint. Oxidation #s are also quite high.

I'd consider trying GC 0w30. Bhvrdr had some pretty good UOAs with that on his B6 S4 which is raced.

Dave

i'm going to have it analyzed when it gets pulled at 35k, so we'll be able to see how it stacks up. GC was the other oil I considered, but general wisdom is that the LM seems to stand up well to the timing chains/fuel dilution in this and the RS4 engine....

Nitration is getting a tad high, which is generally due to incomplete combustion, due to spark propagation and ring seal. Better burning can also decrease the influx of fuel into the oil.

Air filter restriction can cause some turbulence in the MAF and cause the ECU to have difficulty holding mixture. This can cause a bit of additional richness at low throttle.

Except for fuel dilution, Jeff's wear looks better than the two UOAs we have on the RS4 with Mobil 1. However, TAN (acids) are higher, which is not good, along with oxidataion, which is also on the high side. This says that the oil has begun to break down.

Another RS4 owner who used Mobil 1 switched over to Lubro Moly 5W-40 and found some significant reduction in wear and dilution. We're hoping that something similar happens here. Otherwise, there are some non-502 oils like Amsoil Euro 5W-40 and Renewable Lubricants BioSyn 5W-40 that perform much better.