Fuel Octane

[Flash-o-matic]

With your altitude so high in Co. the 85 oct. is probably at least the equivalent of 87 at sea level. Your cylinder pressure at that altitude requires less octane. Have at it Al !!

 

[RadialFin]

You can get low octane racing fuels. The purpose of racing fuel is to provide consistency, not necessarily high octane.

For non ethanol gas of the non expensive racing fuel kind, you might have some options...
1) A marina, typically boats use fuel w/o ethanol
2) Some pumps have excpetions for classic vehicles, you might find some http://pure-gas.org/

That said, if you are racing it's all about passing tech, so if a local fuel station and fuel is specified, that's what you'll have to use.
Lowest octane you can get. Heck, I'd run 80octane in these OHV motors if I could

 

[Kart43]

Al I will guarantee the driver will not tell the difference between 85 and 87, the stopwatch will not show it either. Dryslick in our area the lower octane fuels 85/87 contain 10% the midrange 5% and the high test has no methanol. We use 91 no methanol this prevents the corrosion and the rapid degradation of the blended fuels. We see no performance decline using an octane rating higher than needed in the LO206.

 

[MikeFlipp]

This guy has several videos that explain octane, engine timing, octane vs performance, etc. good stuff and easy to understand.

This video has nothing to do specifically with the lo206 as the lo206 was designed from the get go as a pump fuel engine and you can't "legally" advance the timing of an lo206, using a higher octane fuel will probably hurt your performance not help it.

Dyno Testing Premium Fuel - Octane Level vs Performance

https://youtu.be/gqvhaPLuTPI

 

[rkcarguy]

We had an exceptionally hot summer here this year, the setup that ran great during the winter cost me a head gasket this summer and I discovered signs of detonation on the edge of the combustion chamber near the exhaust valve on my WF motor. Sharp edges left on the edge of the chamber on both the new WF and the used one. Used 600 grit to smooth this edge along with Burris MLS gaskets in .045" and no more issues so far.

 

[MikeFlipp]

Our regular is 85 octane. Is that too low? Also 10%+ of ethanol in any fuel from a gas station. CO state law that it is at least 10%. Our premium is 91 with mid at 87. Altitude is around 5000 feet above sea level.

List of gas stations with clear premium:

http://pure-gas.org/

 

[alvin l nunley]

With your altitude so high in Co. the 85 oct. is probably at least the equivalent of 87 at sea level. Your cylinder pressure at that altitude requires less octane. Have at it Al !!

No argument from me.