Ethanol

How come when I use 10% ethanol that I am advised to go up a grade from 87 to 91 in my lawn equipment. Both 2 and 4 cycle equipment. Should I consider doing this with my '96 grand voyger with 155k?

I can think of no logical reason at all. It makes no sense to me.

up grade to 91 gas for a lawnmow is bad it will burn your valve up.

If you are advised to use 91 octane fuel in your lawn equipment, who makes it, BMW?

Read the owner’s manual for each appliance and use the fuel recommended by the manufacturer.

Toro recommends 87 octane fuel for 2-stroke and 4-stroke engines. They even say that higher octane levels serve no useful purpose.