Oil Test Results

I don't see a thread for oil test results so I thought I'd start one so we can compare oils a bit better. This is the first test in my new-to-me car. It came with LiquiMoly in it which, I understood, has low amounts of Moly in the oil and the results bore that out. I replaced this with Driven DT40 which has higher amounts of Moly.

DT40 will have more moly, higher viscosity, and your wear levels should be lower using it vs the LM (which does not have much moly in it as you noted despite having the word "moly" in their company name and this very often confuses people). There are a few UOA threads on RL that you can look at to see results in the 996 and 997 forums. For example: https://rennlist.com/forums/997-foru...-analysis.html

Here's my last UOA from June this year.

Kent, you may find this thread of interest. Take a look at the oil tests that are posted for comparison of different oils. https://rennlist.com/forums/996-foru...pca-video.html

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What was the oil?

Here are the 1st 2 under my ownership, 04 C4S with 106k at this point. Just changed over to Driven DT40 with plans to continue using that moving forward.

Here is the ussd okl abslysis (UOA) for my '99. This is the first UOA I have taken. My car has 190K miles and still runs well. The oil is Red Line 20W50 with almost 5k mikes on it.

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wear looks good but your 1.45 fuel dilution is way too high for a port injected engine. Try running a bottle of something with a high concentration of PEA and see if it goes down. Are the injectors original?

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My fuel dilation is 2.5 and Lake was ok with it. He did mention that PAO/Ester oils can retain fuel

Ok, I will try the fuel treatment. I switched to Chevton fuel about 10 months ago. I have driven about 7k miles during this time. Maybe the gasoline does not have enough PEA to remove existing deposits? The service records indicate fuel injector replacement but it is not clear if all were replaced or only some. I have put about 50k miles on the car with the existing injectors.

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You explicitly asked and Lake said your 2.5% fuel dilution was ok? I wonder if that was a misunderstanding, I find that hard to believe because that is very high for a port injected engine. While esters do have high polarity, which would increase your fuel dilution all else equal, it should not be 2.5% especially in a port injected engine. To understand the context, do you happen to have your question and his response? Thanks

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I sent Lake an email after reading your post because it didn't sound right and I didn't think he would say that or maybe there was a misunderstanding. This was his response: " A report with 2.5% fuel dilution should have been flagged in yellow as abnormal fuel dilution. I am human, so I may have made an error. 2.5% fuel dilution is abnormal, even if an Ester based oil was a contributing factor to that level of fuel dilution. " My opinion is that a 2.5% fuel dilatation is shockingly high for a port injected engine and should be investigated immediately. Esters are polar and thus will hold more fuel in suspension compared to, say, an mPAO but 2.5% is way, way too high using any base stock.

@silver_tt Hi mate - you're right to question. and I shoudn't put words into Lake's mouth so to speak. I've infered from his response. (question and answer below). I will add that Motul 5w-40 8100 Xcess GEN2 I had a high fuel dilution. However grain of salt that company does not offer the best industry standard of fuel dilution testing. All six injectors removed and tested. One found sticking closed (not open). replaced all six. I also found that oil pressure on 5w-40 was low when pushed hard so.... So I changed the oil and upped to motul 300V 5W-50 Using a different company (ALS) I send 2000km took a sample and fuel dilution was 2.4% using % by GC That's when I emailed Lake. Question and answer below I then did a video recording of fuel trims using PIWIS (the $75 setup) with a YT screen recording and sent to PT3 and he said they all looked ok when I bought the car compression and leakdown were exclent (according to the indie) Now what I can say is that on the same oil at 4000km (I did 1500km over a weekend) the dilution dropped to 2.2 % by GC. I also know that between the 0-2000km range the car was with a mechanic for 3 weeks getting sunroof fixed and knowning where they were (zero parking offsite) the would have, very likely, been starting the car morning and night to move in/out of workshop daily. I also beleive that these cars dump fuel when they first start (why the stink) in order to warm the cats faster (I'm sure I've read that somewhere on here?). And why short trips are highly discouraged along with long idling to 'warm up' vs start, count to 10 and drive gently. Which is what I do. I'm now 14,000km into ownership. The consumes zero oil on the stick or guage Anyhow how, from his response I inferred that PAO/Esters once fuel dilution gets in don't release or burn off once oil temp is high so easily. Justin (PS Rushed post. I'm supposed to be working... the boss is an a$%#hole... wait.. that's me )

Thanks for all that information, super helpful. I see Lake was responding to your question on oxidation, which will be a higher number when using an oil with an ester base stock like you are. Esters tend to have higher fuel dilution because of their polarity. It looks like he missed your question about the fuel dilution. Fascinating that with 6 new injectors (I am assuming you bought genuine Porsche?) and fuel trims looking good the dilution is so high. You leaked it down and it was good so ring seal should be good. Sample error possibly? I am curious if it persists into your next sample but it seems like you had it with your previous sample as well. It is wild to get 2.4% fuel dilution after only 2000km/1200 miles. Even 2.2% is very high. That is high even for a direct injected engine. What you say is true that on cold start the ECU will run rich to heat up the cats as fast as possible. And short trips are not ideal because the engine isn't getting up to operating temp for a sustained period of time. But still I would not expect this to be the reason for such high fuel dilution alone.

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Porsche injectors were $750 each. Bosch were $120 each. I had them tested and came out good. I cannot find a reason for the fuel dilution other than short starts at mechanics. For me this car gets used anytime I need to go 20 min plus. Otherwise I use my A4 or GTI. I'm happy to post up all my oil samples but don't want to hijack this from the OP. Justin ps I missed a previous email from when I had a 2.7% dilution

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Congrats Justin. Sounds like you are doing all the right things!

This thread is 2.5 years old and the OP hasn't logged in for over 6 months. I don't think you are in any way hijacking this individuals thread. You have really tested the gamut of low hanging fruit. The only other things I can think of that are more obscure would be: - Did you buy the injectors from a reputable source? $750 per injector is crazy from a Porsche dealer, I believe they are more like $300 here from a dealer in the US at wholesale pricing last I looked. - I see you are running Nikasil cylinders, which require low tension rings. You could check with the builder or anyone else you know with the same build to see what their fuel dilution looks like. I wonder if it's a byproduct of the build or pistons/ring package. - When you were checking the fuel trims did you do it while the engine was hot or cold? If the viscosity is still good and you don't see high wear then you have a lot less to worry about until you figure it out.

Yeah, I remember Charles talking about the challenges with "new" fuel injectors with all of the testing they have done. Which i why I have always bought mine thru LN knowing that they test them. Unfortunately, every country has its issues with import/export costs, restrictions and availability. Nevertheless, oil testing is critical to see what you have going on under the hood. Without it, it would be tough to know what changes need to be made to address issues.

I have put the Techron fuel aytem cleaner in the tank. So far there is no discernable change (as expected). It will be a while before the next oil change and UOA. As far as the thread-jack concern, this thread was started to share oil analysis data so it seems like it should be ok to discuss related issues.

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@silver_tt ehhehe. I didn't look at the age of the thread. My prices are AUD. The engine rebuild was performed in Australia. At the time I knew about lokasil and issues around bore scoring an that nikasil is preferred. That was the extent of my knowledge. So the engine isn't a Hartech/LN nikasil and I'll leave it at that. Car was bought 116K on the clock July 2024. Now 130K March 2026. Work completed early doors (within 3 months) was * New water pump * low temp thermostat. * switch oil to Motul 8100 excess 5w-40 for the moly content * Plus other bits like fix oil leak from the IMS seal (it runs LN solution but it was pissing out oil here) and suspension etc. Prior to this work I did take an oil sample and there was no fuel dilution. Note however it was a group III+ oil (Gulf) and it was prior to the low temp thermostat and it was using a company that doesn't do % by GC but rather a test that was swing wildy. Ie I questioned one test and after re-testing the value moved dramatically. Hence why I stopped using techenomics and switched to ALS The first oil sample that shows 2.7% % by GC (ALS) was post low temp but also an oil with pao/ester as the base oil. I also had a fuel smell (which turned out to be the filler neck into the tank) I also saw pressure drops on a couple of fast sweeping bends so I ordered FVD X51 style sump (I won't go into why / would have preferred UDIS) and asked the mechanic to test fuel injectors. That's when one was sticking etc.. and I threw 6 new bosch injectors from a reputable porsche parts (indie) supplier here. I also switched to 300V 5W-50 thicker oil for better pressure stability (as recommended by slakker from a thread I started) I do note that in traffic my water temp gauge gets to vertical and not beyond (996.2 so I understand the gauge is less sensitive than 996.1 ?) but I have experienced that at freeway speeds in 30c ambient (86F) that the water temp is slightly under 80c since the low temp thermostat and it will stay like that for 2 hours whilst crusing. re: fuel trims. I only did fuel trims with the engine hot. I ended up buying a druamatic as the PIWIS errors out after 5 min and it is something I've been unable to fix. However the duramatic is a terrible product. It is reporting that my variocams are not moving (they are) and it cannot clear error codes. I've given up and decided I've wasted $500 on that.... So I will try PIWIS again with the engine cold.

No worries about the thread We have good friends from Brisbane. As a control, you could take another oil sample and send it to the same company that said there was no fuel dilution before the work. However if you are saying the test result moved dramatically from one test to another possibly their testing method is just crap and the reading that said no fuel dilution should just be ignored. GC is the best method to test fuel dilution but it sounds like you already know that. Group III base oils are non-polar unlike esters that are very polar, so will hold less fuel in suspension all else equal, but it wouldn't explain going from 0% fuel dilution to 2%+ especially in a port injected engine like M9x. Usually you do check fuel trims while the engine is at operating temperature. It is possible to have a vacuum leak when the engine is cold that seals up at operating temperature and vice versa. That oil filler neck tube is very common to crack as are several parts on these engines as they age. Even if your build is not LN or Hartech that is fine. Those engines just have a lot of data points to compare against. It would be interesting to compare your samples to other builds that are the same if you know of any to see if they also have high fuel dilution. Given that you have Nikasil cylinders you already have a lot less to worry about.

@silver_tt If interested. The right of the red line is the Motul XCESS 5W-40 GEN2. To the left it is 300V that is new sump (hence silicon) and the same oil (which I'm still running) When I hit 130,000 / 7000km on the oil I'll sample again and it is due for a dump/change anyhow Virgin

Yes, the high Si should come down eventually -- that is normal with a sump reseal. I believe the Motul X-Cess 8100 is mainly PAO-based (group 4) whereas the 300V is ester-based (group 5 is a "catch all" but commonly used interchangeably to talk about esters). PAOs and esters are both very good oils, each with their own strengths and weaknesses. It's hard to say much about the wear levels between the two oils in your engine because of the different OCIs (2300km on the X-Cess and more on the 300V) and it is non-linear. The 2.2% fuel dilution is actually trended downward despite the longer OCI. Even at 2.2% fuel dilution you are still at 17 cSt at operating temp which is what matters because that's where your engine is ideally spending most of its time. I do think it would be interesting if there's anyone else from the same builder that they have data on to see if their fuel dilution is also high. For port injected engines you would generally expect under .5%, so 2%+ is a lot higher than that; but you don't need to worry that your oil is thinning and with Nikasil cylinders they are pretty much impervious to scoring absent something like a really bad injector that is pissing fuel down your cylinder wall.