Fuel dilution consequences

[Danh]

My 2015 Honda CRV seems to be a serial fuel diluter. Two Polaris used oil analysis in succession showed fuel dilution of >5%, despite warm temps, hot sampling and mostly-highway miles. The most recent UOA, taken immediately after a 400 mile highway drive using premium fuel, showed dilution of 1.9%. It's hard to imagine conditions less-favorable to fuel dilution than this, so my range seems to be 2% - 5+%. How much over 5% is unknown as Polaris' methodology doesn't measure %s greater than 5.

My dealer ran a battery of tests and found nothing wrong and will do no more (yes, I'm now "That" customer) so I'm sort-of stuck. And perhaps this is just a normal characteristic of the car. Fwiw, the oil used has been Mobil 1 Advanced Fuel Economy 0w20 and the car has 14,000 miles and fuel dilution %s are derived by Polaris from gas chromatography.

Now the question is, "So what?". Within somewhat reasonable bounds, the harm from fuel dilution seems to be reduced oil viscosity. My used oil analysis show 100C cSts in the 6.2-7.0 range so I'm technically in-grade, though I doubt I would be at the end of the 10,000+ mile OCI suggested by the IOLM.

If reduced viscosity is the real issue, could I consider myself "protected" by upping the viscosity? Trying to keep reasonably legal for warranty purposes, a 50/50 blend of Mobil 1 0w-20 and 0w30 is a consideration. Or are there other fuel dilution consequences of concern? We usually keep cars for 10+ years and 100k+ miles, so relying solely on the factory warranty isn't too comforting.

In my personal experience, Honda's combination of DI, 87-octane fuel and 0w-20 oil recommendations and gearing that minimizes revs (and probably maximizes pre-ignition and over-fueling), seems a poor compromise.

Thanks for any thoughts.

 

[Eddie]

The wear values from the UOA are the most important information. What are the wear values and are they unreasonable? Ed

 

[circuitsmith]

Make sure the PCV system is working properly, valve and all passages are clear.

 

[Danh]

Originally Posted By: Eddie
The wear values from the UOA are the most important information. What are the wear values and are they unreasonable? Ed


The sample runs were short, but 3,200 miles showed iron 7 aluminum 4 and copper 2. The most recent sample at 1,000 miles had iron of 2, aluminum of 1 and no copper. While not outstanding, these seem OK especially as some break-in is probably still occurring.

 

[Rand]

Probably fine, You could always sub in 1-2qts of 5w30 to give it abit more viscosity reserve to combat the fuel dilution.

However I doubt its necessary as long as you aren't towing in mountains etc.

 

[addyguy]

As long as wear metals are within acceptable limits, it doesn't matter.

Honda's, of all vehicles, tolerate extremely thin oil 'the best'...why do you think they are pushing like heck for even thinner oils in the market?

Don't worry, just drive on!

 

[CT8]

Have you called Nissan customer service?

 

[DoubleWasp]

Well there has to be a cause to this problem. If there is that much fuel getting into your oil, I'd have to suspect something is causing incomplete combustion of the fuel. I've dealt with carbureted engines that smelled like they were spraying raw fuel from the exhaust that had fuel dilution of >1% after a complete OCI. So what gives here?

Something is amiss. Have you checked your spark plugs to see what they look like? I would sure be giving the engine a good spark plug reading at this point.

 

[AirgunSavant]

Why? Is he trading it in for one? lol!
Originally Posted By: CT8
Have you called Nissan customer service?

 

[Danh]

Originally Posted By: DoubleWasp
Well there has to be a cause to this problem. If there is that much fuel getting into your oil, I'd have to suspect something is causing incomplete combustion of the fuel. I've dealt with carbureted engines that smelled like they were spraying raw fuel from the exhaust that had fuel dilution of >1% after a complete OCI. So what gives here?

Something is amiss. Have you checked your spark plugs to see what they look like? I would sure be giving the engine a good spark plug reading at this point.


The dealer looked at them. The only discovery was that one was 3/4 turn loose from the factory. Tightening the plug seems to have made no difference to fuel dilution. And the odd thing is the engine runs great: quick starts, smooth acceleration, excellent fuel economy...

 

[Danh]

Originally Posted By: CT8
Have you called Nissan customer service?


Did call Honda customer service but as this had already been escalated to the district service manager they were disinclined to get involved. I was hoping someone at Honda would say it was "normal" or "characteristic" or "harmless", but no such luck.

 

[SteveSRT8]

Tuned too rich from the factory. Seen this before. You must find a way to alter the programming, whether by altering the O2 sensor signal or changing a thermostat, etc.

The engine is designed to keep the EGT's low, hence the rich mixture...

 

[Solarent]

Originally Posted By: Danh
My 2015 Honda CRV seems to be a serial fuel diluter. Two Polaris used oil analysis in succession showed fuel dilution of >5%, despite warm temps, hot sampling and mostly-highway miles. The most recent used oil analysis, taken immediately after a 400 mile highway drive using premium fuel, showed dilution of 1.9%. It's hard to imagine conditions less-favorable to fuel dilution than this, so my range seems to be 2% - 5+%. How much over 5% is unknown as Polaris' methodology doesn't measure %s greater than 5.

My dealer ran a battery of tests and found nothing wrong and will do no more (yes, I'm now "That" customer) so I'm sort-of stuck. And perhaps this is just a normal characteristic of the car. Fwiw, the oil used has been Mobil 1 Advanced Fuel Economy 0w20 and the car has 14,000 miles and fuel dilution %s are derived by Polaris from gas chromatography.

Now the question is, "So what?". Within somewhat reasonable bounds, the harm from fuel dilution seems to be reduced oil viscosity. My used oil analysis show 100C cSts in the 6.2-7.0 range so I'm technically in-grade, though I doubt I would be at the end of the 10,000+ mile OCI suggested by the IOLM.

If reduced viscosity is the real issue, could I consider myself "protected" by upping the viscosity? Trying to keep reasonably legal for warranty purposes, a 50/50 blend of Mobil 1 0w-20 and 0w30 is a consideration. Or are there other fuel dilution consequences of concern? We usually keep cars for 10+ years and 100k+ miles, so relying solely on the factory warranty isn't too comforting.

In my personal experience, Honda's combination of DI, 87-octane fuel and 0w-20 oil recommendations and gearing that minimizes revs (and probably maximizes pre-ignition and over-fueling), seems a poor compromise.

Thanks for any thoughts.


Fuel in oil is not a good thing - partly for viscosity going to thin but also can negatively impact the additive package - I would continue running used oil analysis until you determine what a "appropriate" OCI is for this engine. You are right the 10000 mile OCI may not be appropriate. I would look for Fuel Dilution % over the life of the used oil analysis, KV100 so you can tell if it stays in grade and then the elemental analysis for additive concentrations (on the ones that show up) and wear metals. This is a perfect example where keeping a used oil analysis record of every oil change will tell you a lot as you look at the trends surrounding this engine. What you want to look for is drastic changes in the elemental analysis or the oil falling out of grade. If the oil falls out of grade, then look for a blend or change the oil to a 5W30. If there is a spike in wear metals, investigate what might be breaking down, and as far as fuel dilution goes maybe see if you can find a lab that has better precision at levels above 5%.

Also because this vehicle is still under warranty I would discuss your plan with the District Service Manager you have contact with and make sure if something goes wrong that they will see it as warrantable. Everything may be fine and you may run 100K+ miles with no issues, but this also may be a case where paying the 25$ for used oil analysis at each oil change pays off big dividends if you catch an issue and get it fixed before a catastrophic failure. Polaris or the used oil analysis lab should be able to provide you with a list of wear metals matched to common engine components that you can get the dealer to check if a spike occurs.

 

[UNC017]

Originally Posted By: AirgunSavant

Why? Is he trading it in for one? lol!
Originally Posted By: CT8
Have you called Nissan customer service?


I assumed CT8 was making a joke along the lines of "it must run as pig-rich as Nissans are notorious for doing."

 

[Kawiguy454]

Is it possible one of the injectors is leaking down after shutoff. If so i would expect an odd startup flutter sometimes. and a long trip would bring the % down as you noted.

 

[Revving2Redline]

If you get on Mobil 1 website,0w20 or 0w30 is suggested. Try 0w30...It could be just the trick.

 

[Danh]

Originally Posted By: Kawiguy454
Is it possible one of the injectors is leaking down after shutoff. If so i would expect an odd startup flutter sometimes. and a long trip would bring the % down as you noted.


I had the same thought, but I'm told that the on-board-diagnostics would detect a leak and nothing was noted by the dealer. A traditional "leak-down" test evidently isn't possible with the high pressure inherent in a DI engine. And no start-up flutters or "clouds of white smoke" (as my dealer told me to watch for).

 

[Danh]

Originally Posted By: Marco620
If you get on Mobil 1 website,0w20 or 0w30 is suggested. Try 0w30...It could be just the trick.


Saw that, too. But I can find Honda approval for 0w30 nowhere else except in Europe and that approval is not for the DI engine. I did ask Mobil where the 0w30 reference came from and they mentioned one of the aftermarket equipment associations. The fine print on Mobil's page says to always go by manufacturer's recommendations, so the 0w30 doesn't seem a "legal" option.

 

[dblshock]

I'd go to a heavier oil and 6k oci's for now..then run a used oil analysis in a year..if it hasn't resolved itself go after Honda with your best effort..is this a 4 or 6 cyl.?

 

[Danh]

Originally Posted By: dblshock
I'd go to a heavier oil and 6k oci's for now..then run a used oil analysis in a year..if it hasn't resolved itself go after Honda with your best effort..is this a 4 or 6 cyl.?


2.4 liter 4 (K24W). So no cylinder deactivation. Actually seems like a great engine except for the fuel dilution. Going heavier is tempting, but with the warranty...