If you can smell gasoline on your dipstick, are you causing increased wear? Does some fuel evaporate out of the oil during normal running or extendeded driving if more isn't being added? What percentage of fuel dilution causes increased wear? Would you say engine oil is fairly tolerant to fuel dilution or not?
Fuel dilution - how harmful, how much wear?
- Thread starter ledslinger
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How will you measure wear? And when? When oil was changed at 3,000 mile intervals, no issues with dilution and I suspect worn out carburetors would subject engines to way more excess fuel than modern injection systems. This fuel dilution thing only came out the last 20 years or so with the push for 5,000, 7,500 or 10,000 mile oil change interval suggestions, or oil life monitors that suggested the same.
It is a problem with some engines, not only limited to extended oil change intervals, although they certainly don't help. One Honda Accord 1.5L turbo that I rented gained almost a quart of oil during my week long rental. It was warm out, I drove it on the highway quite a bit, and yet the oil level increased.
The oil is neither tolerant or intolerant of the fuel dilution. However, the oil's viscosity will be affected. Would I be concerned if the Accord was my car? Of course! I'd probably use a 5W-30 oil instead of the 0W-20, I would also change the oil frequently.
Yes the fuel evaporates, at some rate. Clearly, the Honda's rate of evaporation was insufficient for the crankcase filling "blowby". But even if it evaporates at a high rate, there are remnants of the fuel circulating in the oil. The oil change is the only way to remove those contaminates.
There is a reason certain engines are experiencing early timing/balancer chain failures. Low viscosity is chief among them.
The oil is neither tolerant or intolerant of the fuel dilution. However, the oil's viscosity will be affected. Would I be concerned if the Accord was my car? Of course! I'd probably use a 5W-30 oil instead of the 0W-20, I would also change the oil frequently.
Yes the fuel evaporates, at some rate. Clearly, the Honda's rate of evaporation was insufficient for the crankcase filling "blowby". But even if it evaporates at a high rate, there are remnants of the fuel circulating in the oil. The oil change is the only way to remove those contaminates.
There is a reason certain engines are experiencing early timing/balancer chain failures. Low viscosity is chief among them.
I think you can blame direct injection as the major cause of fuel dilution. Ran 12,000 mile oil changes on a throttle body injection vehicle with no hint of fuel smell on the dipstick.
In the diesel world, IH used to consider a percent or so of fuel dilution in the oil an issue. Once the terrible Maxxforce engine was foisted upon us, these multifaceted turds with fuel dilution only one of the problems, the standard for concern raised to ten! percent. I don't think that fuel resistant bearings were incorporated into the design. Don't want to deal with warranty oil dilution claims? Raise the standard. Ours would gain a gallon sometimes on a 30 qt. sump.
Labs seem to suggest 5 percent as a cause for concern. I would not go by smell.
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It doesn’t matter, I’ve seen UOA posted here showing near 10% and comments indicate no concerning wear. Although I hear a lot of theoretically sound arguments on why it’s harmful, nobody has been able to show how it practically affects anything. When a high mile DI car is posted, they say it’s irrelevant because highway miles are easy on oil. People here often cite this example of “what if you short trip 5k miles a year”, well then if you keep the car for 30 years you’ll get to 150k miles and still likely be trouble free.
I would encourage those that think fuel dilution/fuel in oil "doesn't matter" to dump 1 cup of fresh gas into their new oil next change. There is simply no way this is not harmful at some level (that's where the dicussion starts) vs. not having that fuel in there. Most modern cars have minor fuel in the oil at the end of a change cycle. Folks are using UOAs to justify it not being an issue but UOAs aren't going to show the harmful effects of egregious fuel dilution I'm afraid...
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Minor and egregious seem to be very subjective. What is minor dilution and when does it become egregious? Am I dumping 1 cup of fuel into a 4qt sump or a 6qt?
Does it matter? Just dump a cup of gas in the sump. It's going to nasty it down pretty severely either way.
Where does soot and ASTM D8279 come into play here ?
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The only way you will know if you are causing wear is if you have several, repeated, with same oil, UOA's that show a trend of high wear particles, and even then, it may be just your engine and that is considred normal.
I live with fuel dilution of 4-5% in the honda's. That is why I run a higher grade of oil, (5w30), and I change it every 4k miles. 20$ for 5qt and a 4$ filter isn't that bad, and I haven't seen any excessive wear, as a matter of fact, the wear is VERY low.
Fuel dilution most likely becomes a problem when you run long OCI's up to 10k miles, or let the engine sit with fuel in it for extended periods of time without driving it. If the vehicle gets driven regularly and oil gets up to good operating temps (not the coolant gauge, I am talking about a nice 30 minute long highway cruise or more) then some of that fuel will vaporize through the PCV system.
Its a matter of how much dilution + how much you drive + trend data.
Although my UOA's show low wear with 4-5% dilution after 4k miles, this doesn't mean that there won't be an issue if I neglect the extra maintenanace. This is why sticking to owners manuals is pointless unless you live in a perfect utopia where engines don't have variance and issues and all drivers drive exactly the same way, in ideal conditions.
I live with fuel dilution of 4-5% in the honda's. That is why I run a higher grade of oil, (5w30), and I change it every 4k miles. 20$ for 5qt and a 4$ filter isn't that bad, and I haven't seen any excessive wear, as a matter of fact, the wear is VERY low.
Fuel dilution most likely becomes a problem when you run long OCI's up to 10k miles, or let the engine sit with fuel in it for extended periods of time without driving it. If the vehicle gets driven regularly and oil gets up to good operating temps (not the coolant gauge, I am talking about a nice 30 minute long highway cruise or more) then some of that fuel will vaporize through the PCV system.
Its a matter of how much dilution + how much you drive + trend data.
Although my UOA's show low wear with 4-5% dilution after 4k miles, this doesn't mean that there won't be an issue if I neglect the extra maintenanace. This is why sticking to owners manuals is pointless unless you live in a perfect utopia where engines don't have variance and issues and all drivers drive exactly the same way, in ideal conditions.
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It must be remembered that the timing belt test was the final test approved and satisfied before SP/GF-6 went forward.
The trend was for thinner, longer lasting oils, that also protect better.
The base stock and add pack are the key.
So I ask, is it the loss of viscosity, or the weakening of add pack strength that ought to be of concern ?
I say dispersents are crucial, as this is what neutralizes soot of small, dense particle size.
My strategy with DI always would be to use thinnest spec'd, highest quality oil, and do successive UOAs to determine how far OCI can be extended.
This I would prefer over the frequent, higher viscosity, standard type oil.
The trend was for thinner, longer lasting oils, that also protect better.
The base stock and add pack are the key.
So I ask, is it the loss of viscosity, or the weakening of add pack strength that ought to be of concern ?
I say dispersents are crucial, as this is what neutralizes soot of small, dense particle size.
My strategy with DI always would be to use thinnest spec'd, highest quality oil, and do successive UOAs to determine how far OCI can be extended.
This I would prefer over the frequent, higher viscosity, standard type oil.
Viscosity loss.
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Yes, no, maybe, Depends
The previosly mentioned Honda 1.5 is direct injected and well known for dillution. Its also a turbo, so whether that matters I don't know.
There are also many, many GDI engines out there with no significant symptoms of dilution.
If anything the old carburetor had to be worse than GDI - however I think low compression and short OCI made it a non problem as well.
IMHO, I think the combination of fine particle wear, the possibility of dilution, and the possibility of oil filter tearing makes short OCI's a solid choice.
Crisis averted as my Dad would say.
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Can you explain this. My small brain is having trouble understanding why starting with a thinner starting point would be better for DI. Not a thick / thin debate - just trying to understand?
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Carbon buildup and oil dilution are exactly not related. However, carbon buildup due to GDI is GENERALLY known to cause buildup in most GDI engines, broadly speaking. Oil dilution is just a boogeyman and not shown to have any adverse effects whatsoever. These people will parrot the same tired “do you think fuel is good in your oil” line, while not being able to actually show any evidence of engine damage or excess wear. UOAs won’t show that though, nor will taking apart an engine, but you should just trust these geniuses with zero proof!
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According to some of the more questionable members' recommendations, it's like you were doing an in-service engine flush!
As Cujet mentioned, timing chain stretch, phaser failures, chain guides, etc all point to low viscosity issues. And as far as wear is concerned, how can you say there is no evidence of excess wear? Even if you ran a UOA every week, you will never be able to discern wear from UOAs since you're only getting a view of <7 micron particles. There's plenty of macro evidence of engine damage and excess wear from fuel dilution, if you're willing to look.
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