J1000
Rising Sun Member
Two things:Better performance and fuel mileage in my FJ62 with less pinging under load. In Kansas City, ethanol free 91 octane can be found at nearly every gas station for about two or three cents more than ethanolized. Here in Colorado it's considerably more and rare in the Denver area.
First if you are getting noticeably better performance just by switching between two different 91 fuels the only difference is ethanol content; that sounds like a mixture issue. Your mixture is likely lean and since ethanol has less energy by volume, using 10% ethanol fuel is reducing fuel ratio even further. Both of these = reduced power and audible knock. My guess is if you are getting audible knock on 10%-ethanol, then your engine is still knocking without, just not as bad. Ethanol content increases knock resistance on top so if you are knocking = lean mixture. I know for a fact that @Cruisertrash's 62 runs super lean in all conditions. If you truck runs lean, yes getting rid of ethanol will "help" but it also is a band-aid not a solution. As you notice it results in lower power, worse MPG, and knocking, and it costs more.
Putting premium gas into an old Cruiser to me is the same as pouring it down the sink. Just a waste. You are spending $10-15 more per single fill-up, that money could be spent re-jetting your carb and getting the engine into a proper state of tune. If you can afford it and don't care, then more power to you I guess. Re-jetting and getting it tuned will result in more HP on 85-octane and better MPG than being poorly tuned on ethanol free 91.
Secondly, ethanol does not "Gum up" carbs. Ethanol frees up old deposits and gunk from the fuel, and that gunk then flows through the fuel system and it clogs things up. The ethanol is only a solvent. If you used exclusively ethanol fuel and a carb-cleaning product every once in awhile, eventually all of your fuel system would be cleaned up and the gumming up would never return. It is possible that by using ethanol-free gas, you are actually contributing and exacerbating to the problem.
Yes, ethanol does contribute to more evap gas and pressure, that is true. Boiling/gas volcano is something that affects nearly all generations of Cruisers. I solved it in my truck by adding heat shielding between the exhaust and gas tank and rebuilding my charcoal canister.
