Fuel Dilution "Burn-Off"

[SonofJoe]

I've been thinking about this all day and I am feeling somewhat uneasy.

In my time, I've formulated billions of litres of engine oil for all parts of the globe. If I'm honest, I've never really worried that much about the field quality of these oils. For the most part, oil is simply oil and it's generally way over-formulated for normal use.

However I have to say that I might be VERY WORRIED if I had a low viscosity engine oil in my car and partially burnt gasoline was already building up significantly in the sump after a couple of thousand miles. My fears would be threefold. Firstly that the viscosity of the fuel/oil mix could drop dramatically. Second, I would especially worried about the HTHS dropping off (gasoline is primarily AROMATIC and therefore will impart a low Viscosity Index) and its impact on main bearing wear. Third, I would be concerned about just how much truly volatile material was making it's way into the oil. In my oil refining days, we would routinely maximise the amount of Butane we could squeeze into Mogas consistent with meeting the maximum RVP spec. If the engine oil were to contain even the tiniest percentage of Butane, then I would fear cavitation attack, most likely of the soft bearing metal. A combination of low viscosity induced wear and cavitation attack, especially if the engine was being driven hard and hot could induce a sudden, catastrophic engine seizure. Not something you want to experience in fast traffic!

I would put these things to Honda. They may deny this could ever happen but VW denied they were using a defeat device right up until it was proved that they were.

 

[doyall]

Originally Posted By: Danh
Originally Posted By: LotI
... A used oil analysis done at 5k miles of oil use showed 2%fuel. ...


Just as a guess, the used oil analysis was performed by Blackstone?


2% fuel dilution is not a significant problem. Having said that, a fuel dilution percentage that has been derived using a poorly interpreted/implemented procedure based solely on the flash point number is pretty useless. (Use the tested viscosity versus the starting viscosity on a viscosity-fuel dilution chart as a rough check. Of course, mechanical shearing and oxidative thickening could impact the tested viscosity result.) I prefer gas chromatography.

 

[SonofJoe]

If you're seeing your sump level visibly rise, and you're not topping up with oil, then you have a serious fuel dilution issue; at least >10%. We used to test for this on so-called 'Aunt Minnie' field tests but I don't recall ever seeing anything as extreme as what's being described.

 

[barryh]

Originally Posted By: Ducked
Originally Posted By: barryh
I have a short commute of 4 miles to work which during winter will produce mayonnaise inside the valve cover. The solution I've adopted is to let the engine breath at the end of the journey by removing the oil filler cap in the garage. It's a real pain to have to do it but it does allow moisture to evaporate off and any mayonnaise disappears overnight. I no longer subject my current car to these short trips but still remove the oil filler on the bike every night without fail.

Would this practice not help with fuel dilution.

I suggested doing that here (with some minor suggested technical enhancements):-
https://bobistheoilguy.com/forums/ubbthreads.php/topics/4284467/Little_Used_Vehicles#Post4284467
based mostly on a discussion on a light aircraft site.

Nobody liked the idea.



They may not have liked your idea but they hardly cited highly technical grounds did they.

All I know is I've been doing it for 10 years on the bike and it works in terms of controlling moisture build up in the winter.
I only forgot to screw the dipstick back in twice and the loud noise of a boxer engine pushing air out the hole will have you shut the engine back down in 2 secs.

 

[FZ1]

Originally Posted By: Danh
Originally Posted By: FZ1
Originally Posted By: KrisZ
The most effective and cheap way of dealing with fuel dilution is to change the oil and shorten the OCI if it is chronic. I've been saying this for quite a long time now.
It especially important when the thin 0w20 oils are used as there is less safety margin for viscosity loss.
This^^^^. + consider a Pela 650 oil extractor and extract the contamininated oil when the level starts dropping. It's easy to do. Leave the filter in place as it only holds about 3-5 ounces.


I have an extractor and have done this. It just seems wrong somehow when the "Intelligent" oil life monitor is saying there's 70-80% oil life remaining. And around here if you confess to a 3,000 mile OCI...
Understand but...When the dipstick level drops I'm extracting it out regardless of miles. When in Doubt...Extract it Out. lol

 

[Danh]

Originally Posted By: FZ1
Originally Posted By: Danh
Originally Posted By: FZ1
Originally Posted By: KrisZ
The most effective and cheap way of dealing with fuel dilution is to change the oil and shorten the OCI if it is chronic. I've been saying this for quite a long time now.
It especially important when the thin 0w20 oils are used as there is less safety margin for viscosity loss.
This^^^^. + consider a Pela 650 oil extractor and extract the contamininated oil when the level starts dropping. It's easy to do. Leave the filter in place as it only holds about 3-5 ounces.


I have an extractor and have done this. It just seems wrong somehow when the "Intelligent" oil life monitor is saying there's 70-80% oil life remaining. And around here if you confess to a 3,000 mile OCI...
Understand but...When the dipstick level drops I'm extracting it out regardless of miles. When in Doubt...Extract it Out. lol


May be an even better reason to extract when the dipstick level rises!

 

[dblshock]

I have to modify my extractor cause a 3/16 od tube wont go in the new dipstick hole, must be elongated like the stupid orange plastic tip

 

[FZ1]

I agree.

 

[FZ1]

My Pela 650 extractor came with a 1/8" tube which works on my 2.4 Accord. Hope this helps.

 

[Ducked]

That light aircraft site I mention above someone suggested (can't remember if they actually did it) heating the oil pan and running dried air through it with an aquarium pump.

This was to combat condensation, and probably overkill for that. Seems like it should work for fuel dilution, though perhaps it'd slightly increase the rate of oil oxidation.

 

[dblshock]

Originally Posted By: FZ1
My Pela 650 extractor came with a 1/8" tube which works on my 2.4 Accord. Hope this helps.


Thank You

 

[dblshock]

Originally Posted By: dblshock
Originally Posted By: FZ1
My Pela 650 extractor came with a 1/8" tube which works on my 2.4 Accord. Hope this helps.


Thank You


specs online say 3/16 & 1/4 like my mityvac

 

[Onug]

So I need an executive summary here. Is the general consensus:
1) Fuel burn-off can happen under the right conditions, but
2) Normal operating temperatures will only allow the more volatile elements (compounds? What's the correct term here?) in the fuel to convert to gas and certain elements will remain behind. Those remaining elements/compounds are technically contaminants.
4) The oil type/weight is not the cause of fuel dilution, but dilution will negatively impact the oil. This impact is most noticeably seen in dropping the oil out of it's specific spec (thinning) and a decrease in the flashpoint.
5) The best way to determine if fuel dilution has reached a point that it's causing damaging is by performing a used oil analysis and looking for elevated wear metals.
6) The used oil analysis should be used to confirm or adjust the nominal oil change interval.

Please adjust/change/correct as needed. This has been a great conversation...and I think a summary is needed.

 

[FZ1]

Sorry,the smaller tube that fits my Accord must be 3/16.

 

[dblshock]

5) The best way to determine if fuel dilution has reached a point that it's causing damaging is by performing a used oil analysis and looking for elevated wear metals.


not just any used oil analysis, a Gas Chromograph test is required to measure fuel amount, make sure that is a part of the program.

 

[FZ1]

Contact Pela to see if they make a tube diameter to fit your Honda. Gonna be a lot of 1.5 turbos out there.

 

[SonofJoe]

Just another random thought on this...

It's been 35 years since I made my last 20kT batch of gasoline. However, as I recall gasoline is generally heavier at the back-end in winter. This is because you can tolerate a lighter-front end in winter and get a bit more Butane into the overall blend.

I only mention this because it's the complete opposite of what you ideally want in respect to fuel dilution. Fuel dilution is more of a problem in winter so ideally you want to compensate for this by using gasoline with a lighter back-end (so that it's easier to strip off). Coincidentally, I read in recent paper (by Shell maybe?) that gasoline with a heavy back-end was implicated in LSPI so maybe it's doubly bad!

If any of this is remotely correct, then it begs the question, do GDI engines need a different sort of gasoline; probably one based on a much narrower boiling range? Whilst there maybe a valid technical argument for this, I'd rate the chances of it ever happening as zero. The norm in most oil refineries is to always 'maximise mogas production' within the constraints of the prevailing specs. In an age where diesel production might be on the wane, this will be truer than ever.

 

[Ducked]

Originally Posted By: Onug
So I need an executive summary here. Is the general consensus:
1) Fuel burn-off can happen under the right conditions, but
2) Normal operating temperatures will only allow the more volatile elements (compounds? What's the correct term here?) in the fuel to convert to gas and certain elements will remain behind. Those remaining elements/compounds are technically contaminants.


Compounds is the correct term chemically but "elements" could also be used in a non-chemical sense, as a synonym for "components", which would also do.

Originally Posted By: Onug


5) The best way to determine if fuel dilution has reached a point that it's causing damaging is by performing a used oil analysis and looking for elevated wear metals.



Perhaps, but there is some argument about how good used oil analysis are at measuring wear, and you'd also have to establish what level of elevated metals was acceptable. If you've always had this problem, you won't have a "known good" baseline to compare against.

Originally Posted By: Onug


6) The used oil analysis should be used to confirm or adjust the nominal oil change interval.


Yes, but again. you'd have to determine criteria. I'd suggest it'd probably be simpler to decide what level of viscosity reduction condemned the oil. Even that might turn out to be controversial, but the lab probably could/would advise you.

 

[Ducked]

Originally Posted By: SonofJoe


I would put these things to Honda. They may deny this could ever happen but....


Don't think they will.

I think they'll ignore/bodyswerve/misunderstand/avoid the question.

Not necessarily in that order.

 

[SonofJoe]

And another random thought...

I half joked about Honda bolting a 'mini steam stripper' on to their fuel dilution prone engines. Realistically this would be impractical. You would keep a separate distilled water reservoir, have a HP steam generator, a condenser, a fuel/water separator, etc, etc. Too bulky, too costly, not going to happen, ever.

However you might be able to remove fuel from engine oil by using something that every engine has; namely vacuum. All lubricant base oils have at some stage been vacuum distilled so it's not like this could hurt the engine oil. You obviously couldn't put the entire sump under vacuum. You would need a means of isolating part of the engine oil and then exposing it to the full intake vacuum (at idle maybe). You might even pull a vacuum purge of air or blow-by gas through the oil to assist the separation & stop the engine surging. The nice thing about doing things this way is the vacuum pulls the evaporated fuel (plus purge gas) to exactly where you want it to go; the intake system, so that it can be burnt.

Surely some of those brainy chaps at Honda could manage to design something as simple as this and make everyone's life easier?