From time to time our government passes legislation not knowing the repercussions that follow. This was the case with the 1990 Clean Air Act. It was passed under the guise of producing cleaner burning fuel by using non-petroleum based oxygenates to create RFG(reformulated gasoline), which would meet the air quality guidelines outlined in the Clean Air Act. Oil companies and automakers argued successfully that their solution, which was a petroleum-based oxygenate called MTBE(methyl tertiary butyl ether) would not require a change in existing cars and would satisfy the guidelines, but was short lived. It was found to be a carcinogen in the 1990's, which led to its demise.
This failure is what lead to using ethanol. The Renewable Fuels Act of 2007 mandated the use of renewable fuels and ethanol became the non-petroleum oxygenate of choice. Blenders received a $.45 per gallon subsidy and trade tariff protection pushed by legislators in farm states aided in the quiet implementation of ethanol in our fuel. Currently E10(10%) is the only ethanol RFG approved for outdoor power equipment.
Small engines both 2 cycle and 4 cycle do not deal well with untreated E10. It can wreak havoc on fuel systems and in particular the carburetor.
"Ethanol has inherent properties that can cause corrosion of metal parts, including carburetors, degradation of plastic and rubber components, harder starting, and reduced engine life," says Marv Klowak, global vice president of research and development for Briggs & Stratton.
Ethanol begins by settling out of the gasoline and attracting moisture, called phase seperation, and concentrates its corrosive effects by destroying rubber and plastic components in the fuel system as well as gumming up the carburetor and fuel lines. E10 can also make the engine run hotter thus dramatically shortening its life.
You can help prevent ethanol erosion by using a fuel stabilizer additive. There are many different brands of stabilizers, but most manufacturers recommend either Startron or Marine Sta-Bil. While using this will help, other steps will need to be taken to ensure fuel related issues do not occur. First, stabilized fuel will not last forever, only pump what you know you will use in a given time period. In the peak of summer even stabilized fuel can start to degenerate in as little 30 days and usually will not last for more than 60 days. You can also find a few gas stations that offer ethanol free fuel which is commonly billed as "recreational" fuel, but you are limited in quantity and be prepared to pay a premium at the pump. Another product available at most outdoor power equipment dealers is called "True Fuel" ethanol free gasoline available in quarts or gallons and is available in 4 cycle or pre-mixed 2 cycle varieties and usually run about $7 a quart and around $21 per gallon. Prevention makes economical sense when you factor in a fuel system repair can cost upwards of $150 or more. Remember even if you are in your warranty period, no manufacturer will cover a fuel related issue.
When storing any piece of outdoor power equipment after the season it is recommended you run the current fuel completely out, add ethanol free fuel(enough to store it with some in the tank), run it for a few minutes to ensure it has cycled through the engine, shut it down, and stow in your shed or garage.