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I have in the past mixed 10% or so by volume methanol with pump gasoline since we only get 91 octane here. Its worked as I expected at the track right after I do it, but a few hours later on the drive home Ive noticed the AFRs are erratic and much leaner than right after I mixed. Right after I mix its typically .3 leaner and I tune for it in the efi, but it goes to a full point or more erratically after the mixture has sat. Will 10% methanol not stay mixed with gasoline? I just did it again here at my house and drove to eat, it ran perfectly, exactly as I expected. On the way home it ran way too lean. Is methanol heavier than gasoline, would it settle to the bottom partially?

Thanks for any insight!
 

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Looking at different articles it looks like a "cosolvent" is needed to keep them mixed, usually ethanol, so maybe my mixture is separating if it has no cosolvent.
 

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Your right....you can mix ethanol alcohol with gas but methanol alcohol does not stay mixed, they do separate.. different animals
 

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so to be clear ethanol is plant based and mixed with regular gas at the pump for our daily vehicle fills? methanol is petroleum based and used more or less for industrial and racing applications? correct or am i high? lol
 

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Phase separation. I'm sure this holds true for any type of alcohol in gasoline.

It is moisture, but also temperature dependent.
 

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so to be clear ethanol is plant based and mixed with regular gas at the pump for our daily vehicle fills? methanol is petroleum based and used more or less for industrial and racing applications? correct or am i high? lol
Definitely go to ethanol if mixing with gas or go to water methanol spray.
 

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you need a stabilizer..... add 0.5% acetone to your mixture total and it will help suspend your mixture . the .ace and ethanol in gas at 10% act as the co-solvent.
the condensation in the fuel tank is going through a phase separation. this is very bad because it breaks up the hydro carbons into clumps of for a simpler term heavy and lite .
this can drive a mixture difference in cyl to cyl. .
please dont add any other oxidizer like nitro's or propylene as it aggravates this condition with lack of detonation resistance.
(BOOM
 

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Ive used mixes of 20% methanol to pump with no issues.

And yes it is perfectly normal for AFR's to appear lean when adding methanol to the fuel. As with an ethanol blend, stioch point is different, so the more methanol you add, the more fuel flow you need to maintain the same overall AFR ( Or lambda, same odds )

But Ive only done this on an EFI car where there are huge volumes of fuel flowing at all times ( ie large flow/return ). So maintaining the mix is no problem

Maybe on a carb car separation might be more of an issue ?
 
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