• All high performance air-cooled engines should have the highest octane you can find. Octane helps prevent spark knock that can easily damage your engine.

• As great as the appeal of non-ethanol fuel may be, I'm not sure you get the same cleaning agents as in the regular "high test" fuels. True, if you're going to ride intermittently over (say for instance) the winter, then non-ethanol would be highly preferable. But during spring and summer when riding time is plentiful, I opt for the less expensive name-brand fuel with the built-in cleaning agents. This is because all fuels leave scuzz in the carburetors, which ultimately needs removal. It just so happens that the ethanol laden fuels simply start to leave deposits earlier.

So as long as fuel is moving through the system, I'd rather have the standard high octane fuel.

You may wish to read this... https://www.toptiergas.com/

Hope this helps.

A Valero near to me has ethanol-free 90 octane. Do you think it's ok for my '84 R65 & '94 R100RT?

Do you think it's ok....

• Do I think that's the highest octane available to you ? No.
• Do I think your engines will sustain permanent damage ? No.
• Do I think the carbs will receive the cleaners they need ? No.
• Would I suggest adding supplemental cleaning agents to the fuel ? Yes.

I'd say it depends. Here in Maine I run the cheapest stuff that Shell or Irving sells. But then our weather is pretty cool and I cruise on fairly level ground and ride solo.
Also I've updated 1981 R100RT with modern valve seats that can handle unleaded fuel.
In fact fuel is so much better generally then 40 years ago that I even run the same kind of fuel in my 1987 GL1200A fully loaded two up in hot Florida weather.

When I can't find that ethanol free gas, I almost always use premium (usually Shell)

When I can't find that ethanol free gas, I almost always use premium (usually Shell)

I'm in Maine too, but I run the highest octane I can get at Irving or Shell. The bike's quite happy, and I don't mind a few extra bucks.

I use what ever boiled boar urine is cheapest in mine. I find Alcohol has zero effect other than decreasing power and mileage. The engine is modified to use low octane despite high compression. In general the higher the compression the higher the octane needed. The octane has to be high enough to prevent detonation or 'knocking' under load. But timing affects this too. If all you can get is low octane and it's knocking retard the timing a bit to see if it helps.

Low compression base gaskets are available for the /5 and using them you can burn anything. Worthwhile if going to Mexico and burning a lot of Pemex.