High Fuel % in Engine Oil - LotusTalk - The Lotus Cars Community
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post #1 of 9 (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 95°C/203°F; coolant temp is 87°C/189°F.

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 9 (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
06 Exige (now rev300 powered!)
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post #3 of 9 (permalink) Old 09-02-2018, 01:59 PM
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The oil won't get that hot with the stock setup.

** save ~10 lbs gain 1 hp ** EQ: Y=(190*X) / (1984-X) where Y is (HP) and X is (lbs)

'07 Lotus Exige S310


WTC 2
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post #4 of 9 (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.

2007 Exige S
Stripped down and turned into a track animal
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post #5 of 9 (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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2007 Exige S
Stripped down and turned into a track animal
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post #6 of 9 (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

2007 Exige S
Stripped down and turned into a track animal
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post #7 of 9 (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 9 (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 9 (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).

2007 Exige S
Stripped down and turned into a track animal
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