Fuel dilution harm and remedies

[Danh]

I have a DI Honda with a fuel dilution (>5%) of engine oil issue. Without getting into the "why" this occurs my question is what's the harm?

From what I've gathered, the primary problem with fuel dilution is reduced oil viscosity that in turn may reduce the thickness of the oil wedge protecting bearings and the like. If this is the case, going up a grade in viscosity (e.g. 0w-20 to 0w-30 or a blend of the two) would keep even badly diluted oil firmly in the OEM-spec'd 20 weight grade. But is this the end of the issue? Obviously, oil is a better lubricant than gasoline but do gas concentrations of 5% or so compromise lubricity enough to remain a problem even if the viscosity is OK?

Appreciate any thoughts.

 

[Warstud]

Idling will cause it to be high.

 

[JHZR2]

I suspect that while you're spot on wrt the hydrodynamic wedge, that at the same time, fuel not only harms the viscosity, but also the flowing properties of the oil (under shear), as well as the additive effects.

I'm not sure if it makes the oil more prone to oxidation, volatilization, etc. In the wash down areas, I suspect that the oil and adds are severely depleted, making the situation worse.

 

[Eddie]

Look at the wear values in a UOA to determine if the values are abnormally high or not. While I have not seen dilution values at ~5%, I have seen 2.5% and the wear values were normal. I think that if the wear values are good then the fuel dilution values arn't causing a problem in the long term. Ed

 

[Falken]

All that is mentioned plus it will raise the NOACK% I would think.

Going to a 0W30 would help a lot but I would look to see if 0W30 or 5W30 are recommended in other markets, as some Vtec valve operation may be RPM/Viscosity related.

A thicker oil theoretically increases the oil pressure.

Also going to a 0W30 would most likely void the engine warranty if the oil spec is a 0W20.

A good compromise may be to use Pennzoil Ultra 0W20 and change the oil under the "severe service" regimen.

 

[Danh]

Originally Posted By: Falken
All that is mentioned plus it will raise the NOACK% I would think.

Going to a 0W30 would help a lot but I would look to see if 0W30 or 5W30 are recommended in other markets, as some Vtec valve operation may be RPM/Viscosity related.

A thicker oil theoretically increases the oil pressure.

Also going to a 0W30 would most likely void the engine warranty if the oil spec is a 0W20.

A good compromise may be to use Pennzoil Ultra 0W20 and change the oil under the "severe service" regimen.


I've been using Mobil1 AFE 0w-20. Do you think a Pennzoil product would handle fuel dilution better?

 

[fdcg27]

Going to a 0W-30 would not void the engine warranty and would likely not have any impact at all. Either the recommended grade or a 0W-30 would meet the same low very low temperature qualification.
Remember, like most makers, Honda recommends an oil grade. They don't require it and unless they can show that the use of an oil outside of their recommendation caused damage, there is no impact on the new car warranty. There's also the issue that no UOA will show conclusively that a grade other than what was recommended was actually used.
Oils can and do thicken in service through oxidation and the W qualification is often lost in service.
This, incidentally, is one of the reasons that we bought a new '12 instead of a new '13 Accord, along with the CVT that came in the later car.
Sticks were all but unobtainable in either model year car.

 

[fdcg27]

Ester basestock oils seem to handle fuel dilution well.
Red Line?

 

[Danh]

Originally Posted By: fdcg27

Going to a 0W-30 would not void the engine warranty and would likely not have any impact at all. Either the recommended grade or a 0W-30 would meet the same low very low temperature qualification.
Remember, like most makers, Honda recommends an oil grade. They don't require it and unless they can show that the use of an oil outside of their recommendation caused damage, there is no impact on the new car warranty. There's also the issue that no UOA will show conclusively that a grade other than what was recommended was actually used.
Oils can and do thicken in service through oxidation and the W qualification is often lost in service.
This, incidentally, is one of the reasons that we bought a new '12 instead of a new '13 Accord, along with the CVT that came in the later car.
Sticks were all but unobtainable in either model year car.




It is interesting that in Honda Owner's Manuals 0w-20 motor oil is a "recommendation" while the rear differential and CVT fluids specified are "requirements". Mobil's website lists both M1 0w-20 and 0w-30 as appropriate for a 2015 CRV.

And good call buying a 2012 and allowing others (like me) to be the Beta Testers for the great Honda DI/CVT transition. You're welcome...

 

[HKPolice]

Gasoline vaporizes at low temps and goes through the PCV system causing carbon deposits on your intake valves. That is the main harm of high fuel dilution, nothing will show up in UOAs. Carbon deposits are unpredictable, some models start showing driveability problems after ~30K, other DI engines are less prone to deposits.

 

[Falken]

Originally Posted By: Danh
Originally Posted By: Falken
All that is mentioned plus it will raise the NOACK% I would think.

Going to a 0W30 would help a lot but I would look to see if 0W30 or 5W30 are recommended in other markets, as some Vtec valve operation may be RPM/Viscosity related.

A thicker oil theoretically increases the oil pressure.

Also going to a 0W30 would most likely void the engine warranty if the oil spec is a 0W20.

A good compromise may be to use Pennzoil Ultra 0W20 and change the oil under the "severe service" regimen.


I've been using Mobil1 AFE 0w-20. Do you think a Pennzoil product would handle fuel dilution better?


The reason I think Pennzoil Ultra 0W20 would help with fuel dilution is it is generally considered on the "thick side" of a 20wt to leave the warranty intact without moving up to a full 30wt.

Mobil AFE is considered to be a "thin" oil in that respect.

 

[Ohle_Manezzini]

Would dilution increase and accelerate the breakdown of longchain polymerization on VII?

Varnish is another issue, maybe the brokendown VII plus base volatization is the source of varnishing. I've seen xw50 oils giving more heavy varnish then in xw30 oils at high temperatures aircooled dilution prone engines from beach buggies.

 

[Ducked]

As I think was pointed out in another thread, the heavy ends of the fuel can gradually build up in the oil and this can reduce its oxidative stability, but an oil change gets rid of most of that.

Maybe do a blotter test periodically.

 

[fdcg27]

It always pays to do your homework before buying something.
By the '15 MY, I'd expect that Honda would have had the DI and CVT issues pretty well worked out.
Still, the current Accords are nothing like the Accords of old to drive.
We think of our '12 as a firm-riding Japanese Buick. There is nothing of the driving entertainment and connectedness that our previous four Accords offered, including the lone automatic.
A reliable and durable car to be sure, but Honda had better get back on its game if it expects to attract buyers younger than our sixty years to its cars. Even we are unimpressed having owned eight Hondas over the past forty years. The first gen Civic was a revelation while the last couple of Accord generations are a disappointment.

 

[paulri]

I'm only asking this, because I don't know, but could fuel dilution of 5% or more corrode/dissolve any seals? If gas is a solvent, would it be strong enough in the oil to do that?

 

[Danh]

Originally Posted By: Falken
Originally Posted By: Danh
Originally Posted By: Falken
All that is mentioned plus it will raise the NOACK% I would think.

Going to a 0W30 would help a lot but I would look to see if 0W30 or 5W30 are recommended in other markets, as some Vtec valve operation may be RPM/Viscosity related.

A thicker oil theoretically increases the oil pressure.

Also going to a 0W30 would most likely void the engine warranty if the oil spec is a 0W20.

A good compromise may be to use Pennzoil Ultra 0W20 and change the oil under the "severe service" regimen.


I've been using Mobil1 AFE 0w-20. Do you think a Pennzoil product would handle fuel dilution better?


The reason I think Pennzoil Ultra 0W20 would help with fuel dilution is it is generally considered on the "thick side" of a 20wt to leave the warranty intact without moving up to a full 30wt.

Mobil AFE is considered to be a "thin" oil in that respect.


Pennzoil Ultra 0w-20 has a 100C viscosity of 8.8 cSt, Mobil1 0w-20 AFE 8.7, so really no difference between the two on that score.

 

[Ohle_Manezzini]

It is still 95% oil and addpack. Would shorten life but no9t to ruin them, like tomorrow.)

 

[Danh]

Originally Posted By: fdcg27
It always pays to do your homework before buying something.
By the '15 MY, I'd expect that Honda would have had the DI and CVT issues pretty well worked out.
Still, the current Accords are nothing like the Accords of old to drive.
We think of our '12 as a firm-riding Japanese Buick. There is nothing of the driving entertainment and connectedness that our previous four Accords offered, including the lone automatic.
A reliable and durable car to be sure, but Honda had better get back on its game if it expects to attract buyers younger than our sixty years to its cars. Even we are unimpressed having owned eight Hondas over the past forty years. The first gen Civic was a revelation while the last couple of Accord generations are a disappointment.


Did that homework. Driveability was fine, no widespread complaints, several model years to get the DI/CVT bugs worked out while in the Accord. That plus Honda's reputation made me think it was a safe decision. But two CVT TSBs and one evidently unsolvable fuel dilution problem later...

That aside, we like the CRV a lot: comfortable, spacious, great fuel economy, solid, etc. Not particularly exciting to drive, but appropriate for the class and type.

 

[KingCake]

Best way to combat fuel dilution is to take it out on the interstate for a 30-60 minute romp now and then. The fuel will bake off, get sucked in through the PCV system and burned.

 

[Danh]

Originally Posted By: KingCake
Best way to combat fuel dilution is to take it out on the interstate for a 30-60 minute romp now and then. The fuel will bake off, get sucked in through the PCV system and burned.


Yeah, except in my case the >5% dilution samples were drawn immediately after a 400 mile mostly-Interstate highway run. Three times. Curious, isn't it?