I can't quite wrap my head around GDI engines and fuel dilution of the engine oil

With DI, you only inject the liquid fuel when the piston is nearing TDC, just before the plug sparks. There's simply much less time to evaporate, and you are pushing liquid fuel into the areas that quench burning, and past the piston rings. Now, if we assume liquid fuel is 100x more dense than vaporised, your fuel dilution issues could be up to 100x worse.
Partailly compressed air in a 12:1 engine might be at 400-600 degrees. Some manufacturers/designs inject a lean mixture early in the up stroke then puff a bit more fuel near the ignition event to create a rich pocket near the ignitor creating a stratified charge (and lower the misfire count).

Regardless, some are "doing it wrong" given the results we are seeing with certain marques.

I do not recall having blatant issues with my 2019 VW 1.4tsi. I also recall attaining stellar fuel mileage.
 
" Regardless, some are "doing it wrong" given the results we are seeing with certain marques."
I'm on my 2nd Hyundai with D.I.--the first was a 2.0L turbo DI, and my current one is a 2.4L NA-- oil analysis on both indicated that neither had unusually high amounts of fuel in the oil (@4000 mile OCIs). Despite various comments to the contrary, Hyundai's seem to have a decent implementation of D.I. The mileage / power on the 2.0 TDI was amazing (wish I'd kept it, but my son needed a vehicle, so he ended up with it). The 2.4 D.I. is OK, but power / mileage isn't nearly as good as the TDI. My next one will be another TDI I think.
 
Just for the recotd, TDI vs pre chamber doesn't relate like gdi/pfi. all diesels inject into the cylinder, its just the location of the combustion area that moves from the head to the piston
 
Just for the recotd, TDI vs pre chamber doesn't relate like gdi/pfi. all diesels inject into the cylinder, its just the location of the combustion area that moves from the head to the piston
@Jetronic. . . my use of TDI may be misleading as I know that VW uses that acronym for their Turbo Diesel Injection. . . . my Hyundai's were / are both gas.
 
Well it was good just before the trip. No leaks.
Consider the possibility of a pint burnoff of fuel and water and the rest?
Gummed up rings? The oil was all full of solubilised varnish and soot. See picture above.
The change to a 10W30 fixed the burn off and sooty appearance. I am sure Summer season helped also.

What is your speculation? - Ken
I wouldn't attribute it to fuel dilution but something else.
 
There's much less time to vaporise the fuel. With port injection you spray into the intake port and fuel sits there on a hot intake valve evaporating off. Then the valve opens and fuel + air rushes into the cylinder, chasing down a piston that's moving towards BDC and then back up.
With batch-fire, yes, with SEFI, the fuel is sprayed as the intake charge is being drawn into the cylinder, so there's a column of air moving down the intake port that the fuel is injected into, which is pretty much ideal for blending and creating that homogenous charge of air and fuel.
 
With gasoline as volatile as it is, and engine operating temperatures as high as they are, and PCV systems doing their thing, how does gasoline manage to dilute the engine oil? It seems like it would get vaporized as soon as the engine warmed up. How come it doesn't? Does it combine with the oil forming a different solution?
Use a good quality synthetic oil and change it around 4000 miles your engine will thank you.
 
Took this picture yesterday . FIT is 1.5 Ltr. w/E.F.I. and the ACCENT has the 1.6 Ltr. w/G.D.I.. Fit has MOBIL1 A.F.E. 0w-20 and the ACCENT is P.U.P 5w-20 . Both are S.P , GF-6A . Have used 5w-30 twice in the ACCENT . Both were S.N.+ GF-5 (?) . Some oil / fuel was burned off after 150+ trip . Around 2/3 was interstate with speed up to 74 M.P.H.. Dipstick read a bit lower . 2nd time this has occurred after high speeds on long interstate drives . :rolleyes:

IMG_9934.JPG
 
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You have 2 different results, which appear to be from the same sample mileage (???). Can you explain? Did OAI just “forget” to report fuel on one of the 2 analyses?
I analysis, fuel dilution was just on another page I think. I don't remember how it printed.
 
IF the oil can get, and stay, hot enough to boil it off, it will dissipate, but often that's not the case.
I have a newer Ranger with GDI and belong to a few Ranger boards and groups. A number of people have mentioned the smell of gas in their oil or fuel dilution in the UOA but if you ask them some questions you find they they are invariably folks who do a lot of short trips and don't put on many miles. Me, my work commute is 20 miles each way and at least three days a week I run 15 miles down the Interstate to our other facility and back. Haven't got a UOA yet but I never smelled gas in the oil either or seen the oil level go UP like some people have.
 
but if you ask them some questions you find they they are invariably folks who do a lot of short trips and don't put on many miles
I drive highway mostly 90% and my gas had 5% oil dilution as per UOA. And no, you will not necessarily be able to detect gas smell with your nose. Why dont you do some UOA instead of using your smell and telling urban tales about others doing short trips
 
Ehhh, is true. Multi-port injection is the present status of addressing that need quite well.

There was no problem with present fuel injection systems.
DI engines should be less sensitive to valve overlap especially with fixed cam timing since the fuel injection can occure during the compression stroke. The late injection timing will also reduce the cylinder wall to fuel exposure.
 
ok,, i had this problem as some of you remembered:

so after some search and tests for 2 weeks the technicians at the dealership say that they will replace again the injectors for free, 2cond time since January probably due to a faulty one ,problematic from new. i know that here were some pieces that were problematic from factory made. they had to produce many pieces since the pandemic closed the factories around world but BMW'S DI injectors were going bad more and more,day by day , month by month fro many owners around the world. so due to increased production ,maybe quality control wasn't always good enough.
now, along with replacing injectors they will replace oils and filter with new,sthing they did't last time in Jan. they think that a lot of fuel dilution is there, something common to bmw's DI engines combined with short trip commute drivers like me.they think this will eliminate the problem for now.
i always did short trips.why fuel dilution so heavy now.i have replaced bad injectors once again before 60.000 km. a friend of mine who wasn't short tripper he did too. i know that its that its a problematic part ,these models engine injectors and not just the way we drive. i am sure of that. but here is my question:

did fuel dilution contributed to bad failing injectors or the other way around? what is the connection with each other?

my spark plugs have 20.000 km running.should i replaced them too? i heard that opinion too,because of bad fuel from bad injectors. and yes i smelled fuel many times.

i have that car for 140.000 km and its the first time i am facing the thing with fuel dilution.car was running motul x-clean+ 5-30 for 11.000 km until now. i filled an extra 1,5 lt during that time .
would an oil with higher grade like 5-40 be better for fuel dilution as i heard many members claim here on bitog?

maybe an ECT causes all these things? should i mention that to the techs?


engine coolant temperature sensor (ECT) issue can flood the engine with gasoline and thinn out engine oil, also will mess with O2 sensor
 
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