Mutul X-clean 8100 C3 5W30 14.100km/6mth Audi S5 4.2 V8 thread #3

Aug 24, 2020
Dear BITOG members,

Continuing my quest for the best lubricant for my car, with the help of Motul I had the X-clean 8100 C3 tested after 14.100 km over a period of 6 months. This topic goes along with my previous thread:

All kg

Moly: 132

Visc @ 100c: 11.49
Flashpoint: yet unknown / being verified
BN: 5.09
TAN: yet unknown / being verified

Silicon: 14

Fuel dilution: 1,5%

First impression is very good. This oil has been in my engine for the longest interval and held up well. Wear again is quite minimal. Moly is higher than factory spec, probably residue of the previous oil (300V). The viscosity hasn't dropped (11,49 vs. 11.7 new) and the BN is still way up (5.09 vs. 6 new). Good news on the silicon which has dropped to the expected levels.

Now for the most important question, the flash point. The new lab hasn't published (or tested) it. I have asked them to see if its possible to get the flash point and TAN numbers for comparison. However they have reported a fuel dilution of 1,5%. I don't know how good or bad that is but according to the lab it's more than we should wish for.

Awaiting further results for the FP and TAN, I am concluding that after 14.100 km this oil held up well with regards to wear and viscosity. Considering it's for half the prices of the 300V and also shows less silicon content, it seems a better choice than the 300V for the enthusiastic street driver. At least, for my car.

Again I discussed these results with Eric, the Dutch representative for Motul. Obviously we can't say this is a clinical results. Many factors are still of influence (the way I have driven lately, the weather, the fuels used etc.). However my base line is that I think my car, which is a direct injection engine is prone to dilute the oil with fuel. My choice of fuel is 98 (E5) and the car is rarely driven in the city or for short intervals. The car does long distances and many of them at 50% WOT while driving 160 km/h on the German Autobahn. But it also sees, perhaps 40% of the time, simple 100km/h stretches at 10% WOT. Also, as much as I try to keep them to a minimum, the car being a road car also sees cold-starts during which combustion is far from optimal and fuel dilution even more prone.

I intend to change the oil around 20.000km and perhaps do an other analysis. I'd be interested to hear your opinions on my last two threads!

Note: the lab erroneously analysed my 5W30 sample thinking it was a 5W40 sample. Therefor were alarmed by the 'drop' in viscosity.


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Very interesting, thanks for sharing.
Silicon is used as antifoam agent, which I could see being more problematic in racing application.
This does seem to be a better option compared to 300V in your application.