Don't let your small engine die a premature death

Killing Your Small Engine

by Rich Finzer

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My beloved 21-year-old chainsaw, "Mrs. Hawkins" (named after my ferocious third-grade teacher), just died. According the mechanic who tried to save it, the culprit was ethanol, the stuff the government wants us to use to help save the planet. It might save the planet, but the jury is still out on that assertion. It did, however, kill my chainsaw. So what's wrong with ethanol? Let me explain.

First, ethanol, which is nothing more than denatured grain alcohol, has the nasty characteristic of attracting and retaining water. Over time, that water will collect in your engine's fuel tank/lines/filter and begin doing serious damage to your small engine, particularly if that engine is an older "pre-ethanol" model like the one in my chainsaw was. Ethanol doesn't mind destroying the engine of your older model outboard motor, snowblower, lawn tractor, or 60s vintage convertible. And the worst gasoline-ethanol blend out there is E10, which is also the most common. Just how bad is ethanol for a small engine? Well, statute law exempts all airplanes from using ethanol-blended fuel. Why? What's the worst that could happen? As an aside, most piston driven aircraft burn 100-110 octane "low-lead" gasoline specifically defined as "aviation gas."

E10 has a "shelf life" of about two to three months. After that, the alcohol begins separating from the gasoline, forming a second layer in your fuel tank. This process is known as "phase separation." And if you live in a colder climate with damp snowy winters, E10 spoils even faster. Once this happens, the alcohol also begins attracting water, which eventually forms a third layer in your fuel tank. This is particularly problematic for the two-cycle gas you use in your weed whacker or chainsaw, as these devices usually aren't operated frequently enough to use up all of the two-cycle gas you have on hand.

Related: How to Buy a Chainsaw

Over time, your two-cycle fuel becomes progressively more contaminated. And as this happens, ethanol also begins rotting away the rubber or vinyl hoses on your engine, like the fuel lines. Worse yet, that dissolved rubber or vinyl gets sent into the cylinders. When combustion occurs, those contaminants form a gooey sludge, which robs engine performance, damages the pistons, and eventually will destroy the small engine. So what's the solution?

There are several things you can do to prevent ethanol-blended gasoline from wrecking your power equipment.

  • Buy fresh fuel on a regular basis. Unless you have an expansive lawn, ditch the five-gallon gas can and replace it with a smaller one. That way, you'll use the fuel up faster.
  • If your plastic jerry can is several years old, replace it. Most likely the ethanol has begun dissolving the inside surface, putting even more gunk into your gasoline.
  • It may take a bit of searching, but some gas stations sell ethanol-free gasoline. Find one.
  • As winter approaches and you put away your weed whacker/chainsaw until spring, get rid of the fuel in the tanks and refill them with ethanol-free gasoline. Additionally, don't let your remaining two-cycle gas "winter over." Give it to someone who can use it up, or someone you don't like very much.
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  • If there is a small airport nearby, try to buy some exempt 100 octane gasoline there. It's illegal for the airport to fill up your car's gas tank, but you can usually purchase a jerry can or two. It's a bit pricey, but cheaper than replacing your power equipment.
  • Avoid any fuel additive containing alcohol, such as ethanol, methanol (wood alcohol), or isopropyl (rubbing alcohol). All alcohol attracts and retains water.
  • If you own an older antique car, try to purchase 110 octane "low-lead" aviation gas. Many older V-8 engines were designed to run on 100 octane fuel. So blend some 110 with conventional premium grade gasoline. Your engine will have more power and get better mileage. Don't fill the entire tank with 110; it will burn up your valves, but a 50:50 mix works great. It's what I burn in my '63 Pontiac Bonneville.

Saving the planet is important, but destroying your expensive power equipment with E10 creates more problems than it solves.

Reviewed September 2017

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