Isopropyl: How Much Juice?

Dear Ralph:
I’m trying to determine the appropriate quantity of isopropyl alcohol to add to the snowmobile gas tank when I fill. I would like to know how many ounces (or milliliters) of alcohol per gallon (or liter) of gas.
Pierre Parent
Quebec, Canada

One to two ounces per gallon is adequate on a preventative basis (8-16 ml per liter) assuming no ethanol in the gas already, which is already at 12-13 ounces per gallon (128 ounces) at a 10% mixture. Then de-icer isn’t needed, but won’t hurt.
Typically, using an entire 12 ounce bottle (0.355 liter) for a 8-12 gallon fill works out well. That’s what we do at temps below zero (F). Make SURE it is isopropyl, NOT methanol.