High Fuel % in Engine Oil - LotusTalk - The Lotus Cars Community
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post #1 of 14 (permalink) Old 08-28-2018, 09:23 PM Thread Starter
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High Fuel % in Engine Oil

I have seen a sudden rise in fuel % in my oil (per Blackstone analysis it was 1%, recently it jumped to 2.8%, then 3.8%). I change the oil every 2-3 track days, so the mileage is low.

I wonder if anyone could suggest a cause? Here is some relevant background:

This is an '07 Exige S with Blade275 tune (3" pulley, stock fuel injectors and pump, cup air box).

I changed the injectors (they were original).

Leakdown is 2%, 3%, 3%, 2%.

Wide Open Throttle AFR is 12. Idle AFR is 14.

20 minutes into a track session: engine oil temp is 95C/203F; coolant temp is 87C/189F.

I have only low-pressure crank-case ventilation and fuel condenses in my catch cans.

Thanks in advance for any thoughts!
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post #2 of 14 (permalink) Old 09-01-2018, 10:45 AM
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I’m no expert but your oil probably has to get hotter to boil the fuel out of it. I’ve read lot of posts on this and optimum temp seems to be right around 220-240 just so the fuel and coolant will boil out.

I drive my car on a lot of short trips but I try to take it out and get it real hot every now and then. I need to do my black stone oil check. I’m curious to see how healthy my motor is.

Ken
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post #3 of 14 (permalink) Old 09-02-2018, 01:59 PM
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The oil won't get that hot with the stock setup.

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post #4 of 14 (permalink) Old 09-04-2018, 06:18 PM Thread Starter
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Many thanks to both of you. I agree the oil needs to get hotter. I am planning to install the oil/water system sold by elise-spares to raise the oil temps. I don't quite like the open-loop characteristics of the other after-market oil cooling options.

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post #5 of 14 (permalink) Old 05-29-2019, 01:54 PM Thread Starter
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Taking another run at getting some ideas on what might be causing me to get so much fuel in my blow-by:

1) this is certainly a change because there was a time when the fuel-in-oil jumped suddenly
2) I have managed to raise my oil temperatures by converting to a laminova water/oil cooler/heater

I am condensing maybe 100ml of fuel from my blow-by in a 120 mile track day. I have the bigger vent-port routed to a BOE can which I have filled with stainless steel cleaning pads. I have the smaller vent port routed to the low-pressure vacuum port (pre-butterfly/throttle) via a small Moroso Aluminum catch can. I have yet to measure how much is still in the oil.

Thanks!
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post #6 of 14 (permalink) Old 05-31-2019, 04:35 PM Thread Starter
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Alright, f*&k you all, I'm just going to build a new motor and swap it in and see what happens then
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post #7 of 14 (permalink) Old 05-31-2019, 04:59 PM
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My junkyard engines had a fair amount of fuel and oil blowby that varied by condition. I think it was worst when I had a blown headgasket, but you might have noticed other symptoms by now. I also am just going to give up and build an engine.

2007 Exige S with almost every track mod...
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post #8 of 14 (permalink) Old 05-31-2019, 05:07 PM
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Alright, f*&k you all, I'm just going to build a new motor and swap it in and see what happens then
Well you dirty, no-good SOB! Go ahead and build a new motor. Best of luck to you.

San
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post #9 of 14 (permalink) Old 05-31-2019, 05:28 PM Thread Starter
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Thanks San!!!

I bought a short block a while ago and more recently a moderately crazy head from MWR, so here goes. I just hope I can keep this one together for the summer (it has ~15k track miles on it).

The lump will be the last thing I replace in this car (which I bought in 2008 with 5k street miles on it).

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post #10 of 14 (permalink) Old 08-01-2019, 10:42 AM Thread Starter
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I got some thoughts from another Lotus owner: perhaps my habit of letting the car idle for 15-20 minutes as a pre-track warm-up might be causing the high fuel content in my oil. I will do this 4-5 time on a track day (the car is 100% track).

Any thoughts on this from you all? Thanks!!!

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post #11 of 14 (permalink) Old 08-01-2019, 11:17 AM
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I can see how long idle times might cause some oil contamination. The crankcase evacuation system wouldn't be working at peak efficiency due to low intake flow volume, that might cause fuel vapor to condense on a cool engine. Maybe you could try shortening the idle time but replace that portion of the warm-up with the engine running at a little higher rpm; I don't know how your car is built, maybe do a couple of laps around the pits to warm it up.

Back in the 1980s, I crewed on an NHRA dragster, we ran straight methanal for fuel and had terrible problems with fuel contaminating the oil; the only 'fix' we found was to change the oil every 3 runs down the 1/4 mile, luckily we had an oil sponsor. Good luck, I'm curious to hear what you find out.

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post #12 of 14 (permalink) Old 08-01-2019, 11:41 AM
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Quote:
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I can see how long idle times might cause some oil contamination. The crankcase evacuation system wouldn't be working at peak efficiency due to low intake flow volume, that might cause fuel vapor to condense on a cool engine. Maybe you could try shortening the idle time but replace that portion of the warm-up with the engine running at a little higher rpm; I don't know how your car is built, maybe do a couple of laps around the pits to warm it up.

Back in the 1980s, I crewed on an NHRA dragster, we ran straight methanal for fuel and had terrible problems with fuel contaminating the oil; the only 'fix' we found was to change the oil every 3 runs down the 1/4 mile, luckily we had an oil sponsor. Good luck, I'm curious to hear what you find out.
Aside from changing the oil more frequently the other option that comes to mind is some sort of oil warmer. Not sure how practical on a normal track day but they have electric pads usually used to keep a car warm when it is cold out, it might help keep the car warm between sessions. Also not sure how hard it would be to use given the undertray.
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post #13 of 14 (permalink) Old 08-01-2019, 12:30 PM
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Honda has a hot mess on its hands because of oil dilution problems in '17 to present 1.5 turbo 4 engines. Not a recall yet, they don't have a fix.

As suggested above, they say that it's mostly with owners in colder states who do not drive the car in distances sufficient to get to temperature adequate to burn off the fuel, so it condenses and makes it's way down into the oil pan.

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post #14 of 14 (permalink) Old 08-01-2019, 01:50 PM Thread Starter
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Interesting about the Honda problems. I have an oil/water heater/cooler (laminova) now. My oil still only reaches about 100C in a 30 minute track session but it gets up to temp faster. I'll run the oil one more day and retest.

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