Fuel Dilution Pontification

[The_Nuke]

Disclaimer: Yes, I know a UOA would be best, but I aint getting one. I'm more interested in the discussion than I am the truth at the moment. As such, telling me to get a UOA will be a waste of your time. Feel free to do it, just know i will ignore it...and question your reading comprehension.

Here's the skinny: I'm about 3500 miles into an OCI on some M1 HM 10w-30, and the oil smells like its got a lot of gas in it. So much so that i will be changing the oil tomorrow to alleviate my fears it is contaminated with fuel to a dangerous point.

The engine is a 5.7L Hemi with 150K miles on it and no signs of wear above and beyond the norm (no excessive oil consumption; no smoking).

Caveats to consider: The 3500 miles are all highway with lots of WOT operation. When i say lots, i mean excessive. When i say excessive, i mean an insane amount.

Question for the forum: Is it reasonable to believe my peculiar operation during this OCI is to blame for the alleged excessive fuel dilution?

 

[SubieRubyRoo]

Every oil change I've ever done smells like gas to me. Heck, even most new oils I smell smell somewhat like gas. I doubt with heavy usage you've got much, if any, fuel dilution, because the fuel will boil off from the oil at the temps you likely saw in the sump. They got burned as PCV vapors.

 

[The_Nuke]

Originally Posted by SubieRubyRoo
Every oil change I've ever done smells like gas to me. Heck, even most new oils I smell smell somewhat like gas. I doubt with heavy usage you've got much, if any, fuel dilution, because the fuel will boil off from the oil at the temps you likely saw in the sump. They got burned as PCV vapors.


That's what I was thinking too, but then I started wondering if that was even possible...could it get hot enough to burn off without igniting, what would a flaming Hemi look like going down the highway, would speeding up only serve to make things worse by fanning the flames...you know, the same questions we all ask ourselves as we drive along.

I have a catch can on it, and it did fill up quicker than usual, but I don't think that's out of the ordinary given the operating conditions. The liquid I emptied out did seem to be less goopy than normal, but there again, I don't think unusual for the scenario.

I don't know. I'm still going to change the oil tomorrow, as I have to go back on the road and figure if nothing else I can pay closer attention this time to see if it slowly gets that same fuel smell much more quickly or what.

I know, not very good sciences, but I'm more curious than anything, so it'll give me something to do.

 

[SteveSRT8]

One thing to remember is that on this board, despite a lot of discussion, I have yet to see any real damage to anyone from fuel dilution.

And no offense intended, but smelling fuel is nothing. You should know your new gen Hemi dumps tons of fuel in at WOT, really goes pig rich.

 

[Mainia]

Originally Posted by SteveSRT8
One thing to remember is that on this board, despite a lot of discussion, I have yet to see any real damage to anyone from fuel dilution.

And no offense intended, but smelling fuel is nothing. You should know your new gen Hemi dumps tons of fuel in at WOT, really goes pig rich.


I am surprised we don't hear of more cats going bad with all fuel dumping in GDI turbos, and engines like the Hemi above.

 

[Cujet]

Originally Posted by SteveSRT8
One thing to remember is that on this board, despite a lot of discussion, I have yet to see any real damage to anyone from fuel dilution.

And no offense intended, but smelling fuel is nothing. You should know your new gen Hemi dumps tons of fuel in at WOT, really goes pig rich.


I'd disagree. There are plenty of examples of engine failures. Hyundai engine failures come to mind. As do the Ford cam chain failures.

Those failures are clearly oil related and can be mitigated by better choice of oil and more frequent oil changes.

 

[The_Nuke]

Originally Posted by SteveSRT8
One thing to remember is that on this board, despite a lot of discussion, I have yet to see any real damage to anyone from fuel dilution.

And no offense intended, but smelling fuel is nothing. You should know your new gen Hemi dumps tons of fuel in at WOT, really goes pig rich.


Now that you mention it, I do have the tune modified to go rich(er) by 0.5% and 1.0% respectively in the upper two RPM bands, so that's certainly not helping...although those changes were made to combat some KR I was seeing in the data logs...hmmm, looks like I need to do some more Datalogging and decide if that's still necessary at the very least and then go from there...

Thanks!

 

[SteveSRT8]

Perhaps I should have been more specific to Hemi engines with regard to my apparent dismissal of fuel dilution as engine damaging.

Virtually every late model Hemi you check will have some fuel in the oil, and it does not appear to do any damage at all.

 

[CR94]

Originally Posted by The_Nuke
Originally Posted by SubieRubyRoo
... the fuel will boil off from the oil at the temps you likely saw in the sump.[/u][/b] They got burned as PCV vapors.
That's what I was thinking too, but then I started wondering if that was even possible...could it get hot enough to burn off without igniting, what would a flaming Hemi look like going down the highway, ...
Fuel in the oil doesn't literally "burn off" in the crankcase, despite the popularity of that phrase in BITOG. It evaporates there, and the resulting (not-yet-burned) fuel vapor gets sucked into the intake manifold via PCV. Finally it burns in the combustion chamber, along with the rest of the fuel in the mixture.

 

[The_Nuke]

Originally Posted by CR94
Fuel in the oil doesn't literally "burn off" in the crankcase, despite the popularity of that phrase in BITOG. It evaporates there, and the resulting (not-yet-burned) fuel vapor gets sucked into the intake manifold via PCV. Finally it burns in the combustion chamber, along with the rest of the fuel in the mixture.


Alright that solves that mystery then, good deal. Thanks!

Now, what about the flaming Hemi? If I am driving a Hemi down the highway which has just burst into flames, should I speed up in an effort to more quickly extinguish them, or will that only exacerbate the predicament?

 

[CR94]

Originally Posted by The_Nuke
... Now, what about the flaming Hemi? If I am driving a Hemi down the highway which has just burst into flames, should I speed up in an effort to more quickly extinguish them, or will that only exacerbate the predicament?
No, bail out. Hit the EJECT switch.

 

[Skippy722]

Originally Posted by CR94
Originally Posted by The_Nuke
... Now, what about the flaming Hemi? If I am driving a Hemi down the highway which has just burst into flames, should I speed up in an effort to more quickly extinguish them, or will that only exacerbate the predicament?
No, bail out. Hit the EJECT switch.


You need heat, fuel, and oxygen for a fire... going faster will bring more oxygen, but it will also remove more heat. But will it remove heat at a higher rate than it's bringing in oxygen?

 

[PWMDMD]

Originally Posted by Cujet
Originally Posted by SteveSRT8
One thing to remember is that on this board, despite a lot of discussion, I have yet to see any real damage to anyone from fuel dilution.

And no offense intended, but smelling fuel is nothing. You should know your new gen Hemi dumps tons of fuel in at WOT, really goes pig rich.


I'd disagree. There are plenty of examples of engine failures. Hyundai engine failures come to mind. As do the Ford cam chain failures.

Those failures are clearly oil related and can be mitigated by better choice of oil and more frequent oil changes.


The questions are were those failures due to: 1. Fuel dilution?; 2. Improper oil selection?; 3. Improper OCI?; 4. Manufacturing defects?; 5. Particularly hard driving cycles?; 6. Some combination of some are all of these in some engines but not others? Did these cases represent engines that would've failed regardless of fuel dilution but would benefit from different oil selection and OCI and when they did fail due to oil selection/OCI and a UOA was done they just happened to also have fuel dilution?

There are probably a handful of other questions that would need to be systematically studied and answered to come to a reasonable conclusion that fuel dilution caused those failures and represents a real and significant concern for the average driver of those engines. At best we can say those engines had failures and fuel dilution but that's it...we can not say fuel dilution caused the failure. Even if we can determine fuel dilution was the cause we still can't say fuel dilution is bad in all engines....just those engines. There are literally millions of engines with fuel dilution doing just fine with numerous UOAs showing normal wear.

It's why we have the scientific method...lots of things can't be determined by simple observation - many require in-depth investigation.

 

[MCompact]

Originally Posted by SteveSRT8
One thing to remember is that on this board, despite a lot of discussion, I have yet to see any real damage to anyone from fuel dilution.

And no offense intended, but smelling fuel is nothing. You should know your new gen Hemi dumps tons of fuel in at WOT, really goes pig rich.


Same here- much hand-wringing and whining, but no proof of damage. My MS3 was supposed to have an engine that flooded the oil with unburnt fuel. Lots of bed wetters were changing their oil at 3k miles(or less). UOAs on my car indicated that a 7.5k OCI was-if anything-conservative.
And I agree that smell is not a valid test- If I couldn't afford a UOA I'd go with a taste test.

 

[Mad_Hatter]

[
Originally Posted by The_Nuke

That's what I was thinking too, but then I started wondering if that was even possible...could it get hot enough to burn off without igniting, what would a flaming Hemi look like going down the highway, would speeding up only serve to make things worse by fanning the flames...you know, the same questions we all ask ourselves as we drive along.

Gas, E0 and ethanol blend, has a relatively high (like around 300c) flash point (auto ignition). If it didn't it would auto ignite in the cylinder before being compressed.

Have you thought about checking for a leaky injector?

As for your FD, as long as you're using a sufficiently thick oil to maintain a MOFT it shouldn't be a "problem" per se. That's in theory...