Mutul X-clean 8100 C3 5W30 20.000km / 8mth Audi S5 4.2 V8 thread #4

Aug 24, 2020
Dear BITOG members,

To continue my search for the best oil I have come to a conclusion after four different oil analysis. Here are my previous three threads for reference:

Thread 1: Motul 300V 5W30 after 11500 km

Thread 2: Motul 300V 5W30 after 4500 km

Thread 3: Motul X-clean 8100 C3 5W30 after 14.100 km

So, what is the result of the latest analysis? 19600 km and 8 months.
Have a look at the column on the far right, i.e. Oil-C. Bear in mind, Oil-C is the same oil tested at 14,1k and 19,6k. I did two analyses of this oil.

Analysis 1Analysis 2Analysis 3A 4
Gasoline cont
Visc 4067,0666,97
Visc 10011,3411,5911,4911,4
Oil A (300V)Oil B (300V)Oil C (X-clean 8100)Oil C

PropertiesOil-AOil-BOil-COil-C300V factory specX-clean factory spec
Visc 4067,0666,97
Visc 10011,3411,5911,4911,4

I have tried to attach the lab report to this thread. I don't know how to properly present it so it loads right on the page. Perhaps someone can help? I have it in PDF. Mind you, the report reads:

"Operating time since change km 15570" which is incorrect, it should be: 19600 km (I don't know how they misprinted that up, perhaps my German was off..)
"Total operating time km 67113" which is not for the oil but for the engine.

Unfortunately the analysis of Oil-C (i.e. the 8100) was done by a different company. They have not provided some data such as Flashpoint and TAN. I know, it makes the comparison not perfect but oil analysis cost is a factor since I'm just a guy making a living and trying to find out as good as possible what's going on. Also I want to mention that Motul, especially the Dutch representative, helped me on this one. He funded the last two analysis since I expressed my concern after the first two tests.

Discussing the results
Now we can compare three different batches of oil against each other, i.e. two times a 300V and one time a X-clean.

- If we look at wear than the numbers are perfect. Alu, copper and iron are all in the low's. Especially looking at the latest analysis at 19600 km the wear rate is nearly as low as at 11,5k (300V) or 14,1k (X-clean). So top marks for that.
- If we look at contamination, we notice that the 300V, after 11,5k had quite elevated silicon readings. Our first thought back then was that it could have been the air filter. This was changed. The second analysis again showed even higher silicon content. We figured that it might be gaskets being dissolved by the 300V and releasing sillicon. We are quite sure of this if we look at the X-clean that after 14,5k showed a significant drop to normal values and after 19,6k showed the same sillicon numbers as the 300V at 11,5. We suspect that the X-clean is less aggressive to the gaskets used in a factory built street car but the 300V is not 'that bad'.
-If we look at properties than we see that all the oils pretty much retain their viscosity numbers, their VI and BN, even after extended use. The flash point, which was the reason for this whole project, unfortunately was not measured for oil C. The BN in Oil-C after 19,6k still showed quite a high number indicating this oil still has quite some life left. Yes, again, no TAN to compare but this is all I got.

So, what is the conclusion?
The basic conclusion is that Motul X-clean 8100 C3 is a very good oil and exceeds all my requirements for a lubricant. Motul 300V is also a very good oil but, even though it is made from the best base group V producs to the highest spec, it is not optimal for a street application because it is meant to operate at a high temperature, in an engine that will be rebuilt after let's say.. a Le Mans 24h race. Bear in mind, Motul has upgraded the formula since my first few tests with better street application in mind and I heard they were testing it.

If we consider, what is the requirement for a good lubricant in a street car? It needs to keep wear to a minimum at a reasonable cost for a reasonable oil change interval.

Than how did the 300V do? Well, it did good on the wear part but I think an OCI of 10k with considerable cost per liter (my V8 takes almost 9L) makes it very expensive. Also, it could be detrimental to gaskets and there is the question of significanly lower flashpoint. Is the latter a problem? It could quite well be. If the oil gets hot enough and the flashpoint is low enough, burning of oil could result in carbon deposits, oil 'consumption' and perhaps other unwanted effectes. When would this happen? Flashpoint drops due to fuel contamination. I think, a race car engine does not contaminate oil as much as a street car engine. So a race car running 300V will probably not have this flashpoint issue. A road car however, after 10k, could.

Than how did the X-clean do? I think it did very well. Again, the wear numbers indicate nearly no wear at all, even after a oil change interval of 19,5k. The properties show that it still has nearly the factory spec viscosity, VI and base number and it does not seem to be detrimental to gaskets. We cannot compare or even see the flash-point levels so this will remain a mystery. Considering the significantly lower cost as opposed to the 300V oil, I would say the X-clean is to be considered the most optimal oil in my application. Which is a high performance street car. If I change this oil once a year after no more than 20k I am quite sure it will keep the engine in the best possible condition an oil can do.

And the winner is: Motul X-clean 8100 C3 5W30

I would be interested to hear your input on this project and share your opinions. I hope this will also provide some data to back your choices of oil for your car.


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To clarify, the oil referred to as X-clean 8100 C3 5W30 (oil C) is the 'X-Clean+ 5w30 for
  • VW 504 00 / 507 00
  • MB-Approval 229.51
  • BMW LL-04
by Motul.