Winterizing Rules for Ethanol

Engine makers disagree on off-season fuel storage procedures.

The debate began innocently enough. Pierce Hoover, editor of Motor Boating, asked my opinion on winterizing procedures with ethanol-extended gasoline — a fuel much more susceptible to deterioration during storage.

Simple, right? Stabilize the fuel, top off the tank, run it through the fuel system, fog the cylinders, change the oil and coolant (on a closed-cooled engine) and cross your fingers until spring.

To stir things up Pierce also asked Kevin Falvey, our senior technical editor, his advice. Kevin’s procedure was markedly different. He runs the tank close to empty before storage. In the friendly wrestling match that ensued, Kevin sent me the Mercruiser maintenance manual — straight from the shoulder. It supported his position of running the tank low for storage so that, if the gas is contaminated by condensation, there is less fuel to dispose of. And moisture contamination is always a risk as long as fuel tanks are open to the atmosphere.


So I fired off an e-mail to Evinrude, Yamaha and the makers of two popular fuel stabilizers, Sta-bil and Star brite Star-Tron.

“Yamaha’s official position is to stabilize the fuel,” said Martin Peters, spokesman for the company. “[We] recommend our Fuel Stabilizer & Conditioner to be run through the entire fuel system, and then store the tank seven-eighths full to leave room for expansion of fuel from ambient temperatures.”

But Star brite and Sta-bil advise we go for full. “In many places the local fire marshal requires full tanks because it minimizes the formation of volatile fumes in the tank and lowers risk of fire,” said Star brite vice president Bill Lindsey. He cited statements made by Fort Lauderdale, Florida, area marshals.


OK, so Evinrude can settle this question, can’t it? Yeah, right.

“It’s a debate that will never be settled,” said Larry Koschak, Evinrude’s product manager. “The different regions and regulations do not allow a pat answer. Cold environments slow the deterioration process, while hotter climates accelerate the deterioration of fuel. Some storage facilities do not want full fuel tanks. For me, I store whatever fuel is left in the tank. This year it was one-half tank — 12 gallons. I fill the tank before our first outing, so I have fresh fuel as much as the tank will allow.”

I guess that settles it. Or not.


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