Fuel Dilution "Burn-Off"

[Jetronic]

Originally Posted By: Ducked
Originally Posted By: dblshock
ya, we got a mess here.


Probably a bigger mess over in New Diesel Ville, where fuel dilution due to DPF regeneration is a big issue, and engine run-away due to auto-ingestion of sump oil is a real danger. Seems possible diesels are dead in Europe.


Before driving diesel or petrol was a preference thing, anyone could run whatever they wanted without issues. This isn't the case anymore, but the DI petrol engines aren't the end-all-be-all either.

Get a good implementation of a diesel engine and it's like the dpf isn't there, even for short trippers. It makes a HUGE difference if a regen takes 10 minutes or if it takes 25 minutes. Another big difference is a regen every 150 miles or every 500 miles. Get a diesel that needs a regen every 500 miles and finishes 10 minutes after the coolant reaches 70°C and you'll have very little issues. Combine the other 2 extremes and you need to make long trips to have a diesel engine work for you.

I chose these numbers from real world experience, both extremes actually exist.

 

[SonofJoe]

Just stumbled on this...

https://www.google.ch/patents/US9394843

It looks like the engineers at Ford have patented a conception scheme to reduce fuel dilution on GDI engines by putting the crankcase under high inlet vacuum when fuel dilution exceeds a pre-defined threshold. The scheme seems to be focussed on applying the vacuum when engine oil temperature is relatively low and normal 'burn-off' can't occur.

I note that the patent is relatively new (2014 filing) so it shows Ford are well aware of the problems of fuel dilution caused by GDI engines being run in cold climates and in short-tripping mode.

However this strikes me very much as a 'mental' exercise. Usually a patent will cite Example Results which compare Before vs After scenarios and confirm the novel benefits from the invention. This one doesn't which says to me they haven't actual built this thing to confirm how it actually works in practice. My gut feel is still that putting the entire crankcase under high vacuum might create more problems than it solves. I guess we shall see if ever Ford implements this scheme on a future model.

 

[Shannow]

Next ford Patent will be on new crankshaft and camshaft seals after they finish sucking them in 15 minutes and 37 seconds after warranty expires.

 

[dblshock]

Now that I've 'reset' without TC-W3 fuel and back on the cafe spec 0/20 the dilution continues unabated...1 week and 700mi. from half full to over the full mark.

 

[SHOZ]

Originally Posted By: SonofJoe
Just stumbled on this...

https://www.google.ch/patents/US9394843

It looks like the engineers at Ford have patented a conception scheme to reduce fuel dilution on GDI engines by putting the crankcase under high inlet vacuum when fuel dilution exceeds a pre-defined threshold. The scheme seems to be focussed on applying the vacuum when engine oil temperature is relatively low and normal 'burn-off' can't occur.

I note that the patent is relatively new (2014 filing) so it shows Ford are well aware of the problems of fuel dilution caused by GDI engines being run in cold climates and in short-tripping mode.

However this strikes me very much as a 'mental' exercise. Usually a patent will cite Example Results which compare Before vs After scenarios and confirm the novel benefits from the invention. This one doesn't which says to me they haven't actual built this thing to confirm how it actually works in practice. My gut feel is still that putting the entire crankcase under high vacuum might create more problems than it solves. I guess we shall see if ever Ford implements this scheme on a future model.
Just Ford again copying my methods. I made up a catch can on my Taurus V8 and had the valve cover air makeup port capped. This gave me about 7"Hg vacuum in the crankcase when there was high vacuum in the intake manifold. The copied my catch can idea too for their V6 ecoboost turbos. I used a spring loaded check valve on the can that would open when there was no vacuum. It would then drain the can automatically. But the Ecoboost have the "catch can" between the heads and it drains into the crankcase. Bad idea there.

 

[Criticalmass]

If your car is out of warranty, get a catch or oil separator. It will help. A lot of people find that a lot of Blowby isn't oil, it's gas and old mixed.

GDI engines also benefit from oils with high detergent additives.

Some manufacturers claim to have a built in return system for blowby (and they do). Problem is it gets dumped right back into the crankcase, thus adding more contaminates to the oil.

 

[Criticalmass]

Originally Posted By: Ducked
Originally Posted By: SonofJoe
If you're concerned about how re-evaporating fuel will carryover oil into your intake system and cause deposits, use the lowest Noack oil you can get your hands on (something like Amsoil 10W30).



Does that happen much?

I suppose steam from a chip pan puts grease mist into the air, but that's quite a violent, high volume process, and I THINK the grease isn't in the vapour phase, so maybe a poor analogy.

Oil molecules get "knocked" into the vapour phase by high KE fuel molecules??


Yes, and happens more with Direct Injection engines because the Injectors run at much higher PSI than Port Injected Injectors, that causes more blowby.

Again, if you are out of warranty, get an oil separator for the passenger side (unless you are running Forced Induction, then both sides). You'll find that when you empty the can, it's going to be a mixture of fuel and oil and look cloudy/gunky.

It won't stop it completely, but it reduces the effect. The Cheap separators hardly do anything.

 

[Criticalmass]

Originally Posted By: dblshock
I just spoke with the service manager and sent him my UOA, he claims to have heard of the issue but not with any Honda brand motors. this is a large metro dealer...requested a plan to deal with this critical dilution flagged by Polaris after only 4,350mi.


Honda is well aware of it since they offer a service to clean those deposits (valve coking) (or used to) at certain mileage intervals. Somewhere around 30k or 50k. I'm not sure, but a friend of mine had to have it done on his Honda and it was expensive.

 

[SHOZ]

I have a catch can on both sides of the PCV for my turbo motor. Here is a typical collection from both sides. The pre turbo intake can is mostly pure oil and is floating on top in this picture. The Throttle Body side is the rest of the gunk. It is mostly water and lighter hydrocarbons and will evaporate over time. The more humid the atmosphere the more liquid collected.

 

[Criticalmass]

Originally Posted By: Danh
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.
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 UOA and looking for elevated wear metals.
6) The UOA 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.


In addition the the other comments as so as not to alarm readers, the fuel dilution issue is almost exclusively, from direct injection an turbocharged direct injection engines. Traditional port injected engines only suffer from fuel dilution if there's really something wrong, like a bad fuel injector. DI/TGDI engines, on the other hand, seem to have varying degrees of fuel,dilution even if they are working exactly as the factory intended.

So, if you have a car with port fuel injection, don't sweat this too much. If you have a DI/TGDI engine, you may want to get a gas chromotography reading with a used oil analysis. It may not make you happy though...


not true. Port Injected engines running high RPMS can cause the same issue since Blowby occurs due to increased pressure.

The valve coking is not an issue because Port Injection dumps fuel over the valves and cleans residual oil so it doesn't cook. But due to EPA regulations and the closed PCV system that returns all blow-by to the intake. Causes other problems and including fuel dilution. Though the problem is less pronounced. The biggest issue for Port Injected engines is the Intake, throttle body, and MAF sensor can get clogged up. The most visible display of this is a slightly bumpy RPM at idle because the MAF is dirty.

 

[mightymousetech]

OK, what the [censored]? I have been an Acura Tech for 15 years, and we largely work on DI engines now, and have never seen anything like this. I had one TLX that had a very slight fuel dilution issue, but the computer on the car picked that up quick and the car registered a DTC for fuel trim out of spec. Long term fuel trim has to be off by 30% to trigger a code. Turned out the PCM was bad. Changed the PCM, did an oil change and all was good.

I hope that [censored] you put in the fuel has not damaged the HPFP or the DI injectors. Why would you add that to a car that uses such high fuel pressure?

Sounds like you may have an injector that is stuck open when shut off. Does it have long cranks, difficult to start?

This has NOTHING to do with the oil he is using, it is a mechanical fault with the car. This is what happens when engineers try and fix cars.

5 min with the factory scan tool should pinpoint that there is in fact something wrong.

 

[WhizkidTN]

Originally Posted By: Criticalmass
Originally Posted By: Ducked
Originally Posted By: SonofJoe
If you're concerned about how re-evaporating fuel will carryover oil into your intake system and cause deposits, use the lowest Noack oil you can get your hands on (something like Amsoil 10W30).



Does that happen much?

I suppose steam from a chip pan puts grease mist into the air, but that's quite a violent, high volume process, and I THINK the grease isn't in the vapour phase, so maybe a poor analogy.

Oil molecules get "knocked" into the vapour phase by high KE fuel molecules??


Yes, and happens more with Direct Injection engines because the Injectors run at much higher PSI than Port Injected Injectors, that causes more blowby.

Again, if you are out of warranty, get an oil separator for the passenger side (unless you are running Forced Induction, then both sides). You'll find that when you empty the can, it's going to be a mixture of fuel and oil and look cloudy/gunky.

It won't stop it completely, but it reduces the effect. The Cheap separators hardly do anything.


I can vouch for this approach. It basically is what I do on my 2.0T Optima. I will empty about 1~2oz of oily, fuelish smelling fluid about every 4K miles (my normal OCI). I have two OCC (PCV and IC). I haven't gotten anything out of the intake side most likely due to being a DD, I'm not into boost all that much. Except when I want to have some fun (safely of course)!

 

[Ducked]

These people use a heated bypass filter with an evaporator that they claim removes fuel and water from the oil.

http://www.ipu.co.uk/products/oillife-bypass-oil-filter/op15/