What Gasoline Fuel Grade to Use?

[FES74]

Here in the United States, you can sometimes find 15% ethenol gas (also called E-85 gas)

This isn't quite correct - E-85 contains 85% ethanol and can only be used in modern, 'flex-fuel' vehicles that are labeled as such. Never appropriate for a stock FJ40.

You can sometimes buy E-15 fuel that contains 15% ethanol, but in my view, that's 50% worse than regular Ethanol gas that is typically 10% or less. The chain of convenience stores called 'Kum and Go' sell E-15, and it would be easy to use this if you were just seeking the 'cheapest gas' they sold. Beware. Farm states (Iowa) are extra big on Ethanol, so pay more attention for crap gas (there, I said it) in states big on corn farming.

Thanks @SteveH . What we have here is just the regular gas w/ 10% ethanol. Will continue to use it for now...

 

[FES74]

I’ve always run Marvel Mystery Oil in my fuel. It’ll keep your fuel tank from rusting as well. I feel it keeps everything protected with a super thin film of oil. Back when I owned an antique airplane, I ran MMO in that as well. Anyone else?

Thanks @Jetlander. Yup. I've read & watch some materials about MMO after i've read your post and it seemed this could be an answer to my current quest. I ordered one already. Thanks again.

 

[FES74]

Keeping drunken-gasoline away from humidity will help keep it from absorbing water?

Having a jerry can, or two, at home might help keep humid air out, by keeping the tank topped up? The plastic Blitz one doesn't appear to vent, but maybe it has a limit?

I'd bet that most of the tank rust experience on FJ40s was due to derelict conditions, but, that is just a wager based on a hunch.

I'm more concerned with the stock fuel pump, and anything soft, that is aged faster due to the modern buzz.

IIAC, the non-ethanol formula was really low in octane, and really high in price (double), here in town.

Thanks for your additional insights @Dizzy . Yup , keeping the tank topped up is one of the few solutions to the rust problem.

 

[FES74]

Some of the antique motorcycles that I've had over the years used to say in the owner's manual to add "upper cylinder lubricant" to every tank of gas, so I used MMO for that for a long time. Nowadays, I will put a bit of diesel fuel in most of my gas tanks every now and then, at least those with carb'ed engines.

I've read and watched materials on MMO after I've read your post and it might be a better option. Thanks a lot @1911. I ordered one already. Appreciate your help.