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Oil Maintenance/Contamination

Ethanol & Flex Fuel Tuning

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Discussion and questions related to the course Ethanol & Flex Fuel Tuning

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I was wondering if anyone could offer advice or share their experience on how ethanol blends affect the oil in their applications. A couple of friends of mine have moved to a 50/50 Methanol/Petrol mix in their dedicated drag cars and I'm helping them and learning along the way. My car is nearly complete and I will be following suit soon.

My question really is how often should they be looking to drop and replace the oil. Obviously both are worried about contamination of the oil and consequential engine damage but this means they are swapping it roughly every event to be on the safe side (after maybe circa 10 passes). If that's what it needs then so be it but I thought I would ask in here for some science and facts rather than generic internet hearsay, to see if this is overkill or about right? Also where do you stand on boiling off the methanol in the used oil (E.g. via a chip pan/earn) and reusing it. Is this a thing or should it always be fresh?

I appreciate there are some variables here. Both are VR6 engines of difference flavours on 2200cc injectors with one reaching around 800-1000bhp at around 55-60% max duty cycle if that helps at all.

We're also exploring pan heaters for the sump which can be run for a few hours in the morning for example to try and remove any meth from the oil. But TBH its difficult to tell how effective this is.

I assume on road cars using pump E85 service intervals are more frequent but obviously these cars are only running a few miles rather than a few thousand.

Any help greatly appreciated.


In the US it is common to send racing engine oil for analysis, you get back a report with details on any contaminants -- that should provide the real answers.

Here are a couple of places in the UK that might be useful:




Thanks David that's ideal. That's the proper 'science' I was after.

I'd still be keen to hear anyone else's experiences in this area or if they've done similar too.


As David suggested testing oil from your application will give you the best information to decide from.

Your experience will be unique per built engine, and vary as the engine wears over time.

With stock engines I suggest a reduced interval from the OE suggestion regardless of fuel because OEMs are basing intervals on what gets them CAFE credits, and reduces claimed cost of ownership, rather than optimizing engine longevity. For example 3k miles vs. 7k is a common suggestion, but I don't shorten it more drastically on E85 unless it's a built engine, race car, or in a very cold climate experiencing lots of extended warmups.

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