For those who don't know about it:
The RS4 is hard on oil and suffers from fuel dilution (gas getting in the oil). The vapors from this new concoction are passed through the PCV and back into the intake manifold where they pass through the valves. This mixture of oil vapors and gas vapors lowers the flashpoint of the oil and it burns on reentry into the motor right onto to the back of the valves.
How is this cured? Well, RI A6, previously RI RS4 developed a new oil with the help of Terry Dyson and Renewable Lubricants, Inc. It's called Biosyn 5/40 and is supposed to be able to handle all that the RS4 motor has to throw at it.
I like the idea but would still like to stay with an Ester based oil. So I went and discovered that the recommended oil for the RS4 is not a 502.00 but it's a 503.01 (longer service interval oil). So I went about looking at the differences between the types trying to find the best oil for my motor, short of the Biosyn, which I am not opposed to using, but just want to exhaust all options before I make the move.
In doing some internet research, I came across this from a Wiki page:
Motul discontinued their 8100 E-tech 0W-40 (VW 503.01) Synthetic Ester oil which was a favourite anmongst the TT community and have replaced it with 8100 X-lite 0W-30 Synthetic Ester oil (VW 503.01). I had my doubts at first because of the lower viscosity at 100 deg C.; 30 instead of 40. This would suggest increased engine wear at elevated temperature but to be fair the Audi recommendation was for a 0W-30 Castrol product originally - but was I protecting my chipped engine more with a 40 rather than a 30? At least 0W for both oils has the same cold start performance.
So why did Motul do this? I rang Opie oils to find out and spoke to Guy.
Guy explained that the X-lite 0W-30 is a more stable oil. The 0W-40 had a higher addition of "viscosity index improvers", in order to achieve the multigrade performance. These addatives are long chain molecules which are coiled up at low temperatures but open out into long chains at high temperatures, in order to increase the viscosity - so it doesn't thin out so much when hot. The problem is that these long chains shear, under mechanical stress, so that before 10k miles is up, a 0W-40 may have decreased to 0W-30 anyway. The X-lite 0W-30, on the other hand, will still likely be close to a 0W-30 in the same mileage, as the amount of viscosity index improvers used is far less. Synthetic oils require far less viscosity improvers to achieve the same multigrade performance than organic oils. In fact the synthetic base stock oil is around 0W-20 and that's the grade that tends to be used in F1 racing. Higher engine speeds require lower viscosity. So it's swings and roundabouts to some extent: Higher engine speeds require lower viscosity but increased loads reqire higher viscosity.
Apparently Motul have improved other aspects of the oil and required to reduce the viscosity improvers in the process. It's still VW 503.01 spec approved and is recommended for the TT specifically.
I have put in a request for an oil recommendation from Opie Oil UK. I also discovered that if you go to Motuls, Liquimoly's and a few other European websites, they all recommend the 503.01 5/30 oil for the RS4.
Based on what I have learned, I think that I am going to switch out my oil to Motul 8100 X-Lite 0/30 weight.
BTW, any S4 owners reading this should look into a 503.00 oil.
Please chime in with your opinions, questions, criticisms and whatever else you may have to say about this issue.
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Originally Posted by VVG
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