I am thinking of the Honda 1.5 Turbo, which is the current poster child for dilution. The consensus from BITOG is that an oil change in the 4-6,000 mile area will do the job just fine. You might want to look at my other post in this thread. If 1,000 miles is all you can get from any oil, there is no magic multiplier in going up a grade.
is there any benefit of going 'thicker' if uoa already checks out?
- Thread starter apollo18
- Start date
I got 4-5% oil dilution at 7k miles and it was the same at 3k miles same driving style. Similar viscosity drop by 2.2-2.4 cSt. The fuel dilution stabilizes at some point. Fuel dilution is not great with any viscosity, but higher viscosity at least keeps it within manufacture recommended grade.
I'm of the belief that film thickness is only as good as the minimum. Increasing film thickness beyond what's necessary is just wasted. I also think the MOFT for many daily commuter engines is a bit lower than its made out to be. If we were talking endurance race engines, running sustained 8000+ rpm and 280+°F oil temps, then fair discussion. For a daily commuter though, that rarely (if ever) sees wide open throttle, you could probably go down a grade and still not be taxing the MOFT. (not that I recommend doing that)
I’d agree with that. But “wasted” is subjective, with fuel dilution and the length of time I keep my cars I’m not concerned with a small decrease in fuel economy.
I still think a better quality oil does more good than just increasing viscosity. I would rather have an oil that starts at 8.8 and ends at 8.0 (no shearing) with 5% dilution than I would one that starts at 10.0 and ends at 8.0 with the same dilution. If the higher viscosity has that much permanent shear, you know there's more temporary shear under load that's happening as well. Which oil is actually more viscous under load? Just because an oil has a higher HTHS in virgin form doesn't mean it'll stay higher with use.
Well, yes, I do use a high-quality oil. But that won’t resist simple dilution any better than any other oil. Yes the VII won’t experience cleaving as much but there’s no way of getting around diluting the oil with a low viscosity fluid. A monograde oil with no VII would experience the same problem here.
And to answer your question, the one that is more viscous under load is the one with the higher HT/HS.
dnewton3
Staff member
This entire topic is just beat to death because most folks are unwilling to agree/acknowledge the fact there is no 100% answer for all situations. When the question is flawed (poorly defined, unbounded ...), then resulting answers are just as bad.
The following things play into lube selection
- environment (temps, altitude, etc)
- OCI duration
- commitment (or lack thereof) to proper maintenance plan (not over-doing it, but not ignoring it either)
- operational factors
- contamination issues (fuel dilution, silica ingestion, etc)
- historical predominant issues specific to the engine series (fuel dilution, soot monster, etc)
Some engines are nearly impervious to grade selection; they just don't care. Other engines are somewhat sensitive to grade selection; the factors above can exacerbate the grade conundrum.
The reality is that while UOAs can help make this determination, the amount of time/data required to ACCURATELY make such a decision is woefully absent from any typical BITOG experiment. I have seen very, very few people here with enough commitment to be patient enough to properly establish averages and trends with truly accurate standard deviation. UOAs are great tools, but they are tools which are easily misused, misunderstood and misinterpreted.
The following things play into lube selection
- environment (temps, altitude, etc)
- OCI duration
- commitment (or lack thereof) to proper maintenance plan (not over-doing it, but not ignoring it either)
- operational factors
- contamination issues (fuel dilution, silica ingestion, etc)
- historical predominant issues specific to the engine series (fuel dilution, soot monster, etc)
Some engines are nearly impervious to grade selection; they just don't care. Other engines are somewhat sensitive to grade selection; the factors above can exacerbate the grade conundrum.
The reality is that while UOAs can help make this determination, the amount of time/data required to ACCURATELY make such a decision is woefully absent from any typical BITOG experiment. I have seen very, very few people here with enough commitment to be patient enough to properly establish averages and trends with truly accurate standard deviation. UOAs are great tools, but they are tools which are easily misused, misunderstood and misinterpreted.
So maybe we should just go back to the 3month/3000 mile oil change interval
How though? Certain fluids just don't & won't mix and why can't a higher quality oil resist losing viscosity more to fuel dilution than some barely Group III base stock? I'm not a betting man but I can't see in this scenario a top tier oil and the something you'd find at Dollar Tree being equal in this regard.
Thesaurus
Cleave verb
"The axe his father used to cleave wood for the fire: SPLIT, split open, crack open, lay open, divide, sever, splinter, cut up."
I had always wondered where the word "cleavage" came from.
The word comes from Viscosity Index Improvers.
Last edited:
For some honda engines it might make sense if you got time and resources
If your question is directed to me, the my UOA is posted in the UOA section
The question was for apollo 18, the OP.
Here is 2.0T Honda with 0w-20 Mobil1. Last OCi only had 3400 miles on it, drop from 8.8 to 6.6 сSt.
Mobil1 0w-20EP 3.4k mil; Acura RDX 2020
80-90% highway driving, 3400 miles (60% oil life left as per OLM). About 5 month. Mobil1 Ep 0w-20. Fuel dilution got worse compared to my last analysis 7400 miles. Car is stock, and regular driving I can't change oil any more often, viscosity has to go up
bobistheoilguy.com
Both motor oil and gasoline are non-polar hydrocarbons and are miscible. When liquids are miscible, it means they will combine at any concentration without separation.
Yes a better multigrade oil with better VII will resist the temporary or permanent degradation of the VII by fuel but after that it’s the simple physics of viscosity. This is the primary means of lowering the viscosity from fuel dilution.
UOA results are quite worthwhile for trend monitoring and for detecting known issues.
Here is an example of how 0W-20 oil performs when not up to the task, 62,000 miles, 500cc cylinders, x-large rod bearings, and 66HP per cylinder. Turbocharged and Supercharged engines do load rod bearings heavily. Here, a UOA might detect the impending doom, if you have a trend or a known issue/metals to look for. The good news is, changing rod bearings is not all that hard here.
The bad news is that a one time UOA, may only show slightly elevated metals here, and could easily be ignored. That's the crux of the problem. Knowing what the UOA is saying. Remember, it is not at all unusual to see high metals, disassemble, and find nothing wrong and no significant wear.
What do you surmise Honda engineers would have to say about this ?
Would they be shocked ?
Would they be surprised and concerned about their engines running on spec'd 0W20 and becoming thinner from, from , from the sneak attack from FUEL DILUTION ?!?
As we move from the theoretical into the real world, what about all those engines that hold up, in spite of using very thin oil and experiencing fuel dilution ?
From the lab to the roadway...
From the lab to the roadway...
