Always use the 93 octane or the highest octane gasoline available for your lawn mower and it will always run good...Here in my area the 93 octane gasoline has no ethanol which ethanol will kill any mowing equipment IMO...
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That's one of
those discussions
A friend and coworker of many years takes jerry cans to other counties that do not have an ethanol mandate for his lawnmowers and old motorcycle.
From my p.o.v I use 87 octane in everything and have no choice but to use E10 - that's all there is. The only thing bad about it is the shelf life is very limited, maybe 6 months. I never let fuel sit in any of my lawn and yard equipment - run it dry before storage. Even when it gets a little stale I just toss a can of Seafoam in there - half can for 5 gallons and it's off to the races. I've had carbs apart on my lawn mowers and tractors and never found any evidence of .... anything really. Clean, rubber lines intact.
The Harley requires 92 octane from the factory so it gets the 93 that's available. It gets stored on fresh fuel with Seafoam and sometimes I even siphon the tank dry at the start of the season just to give of more fresh fuel. It's fuel injected and after 17 years of this is a happy camper.
The 'vette has a .030 over 350 small block in it, old camel hump 2.02 heads. Originally an 11:1 motor that's probably squeaking out a tad more from the overbore. I have no way to easily calculate the compression ratio but it shows a solid 215 psi per cylinder +/- only about 2-3 psi so it's tight as a drum. I'd normally expect to see maybe 180-185 psi per cylinder on the family station wagon. The previous owner - who didn't do the work - spoke of what a horsepower monster the thing was and lamented the lack of 100 octane gas. Because that's what they said to get rid of him. Comparing today's gas with the old stuff is a bit of apples and oranges.
It took me a long time to figure out what was wrong with the thing and in the end - relevant to talking about gas - it was a series of small things that added up that weren't immediately obvious. Timing, vacuum, distributor. So I've got that little pressure cooking cruising perfectly with zero detonation on 93 octane E10. I've been through the Holley 4160 carb and fuel lines, pump, filters more than once for other reasons. I dunno, it's gas, it works and doesn't do anything bad I can tell. I could get 100 octane aviation fuel - from one of the grass strips that those verdammit Hudson Valley Wave UFOs came from - but haven't found the need yet.