An increase in the amount of ethanol in your gasoline won’t hurt your lawnmower…if it’s a push-reel. Otherwise be prepared for big repair bills.

While that sounds alarmist, the threat is real. This fall, the Obama administration will, through the EPA, likely approve a change in federal regulations that will allow gasoline retailers to increase the “blend rate.”

The blend rate refers to the federal rule that limits ethanol blends to no more than 10% for standard automobiles. Commonly known as “E10,” the fuel contains 90% gasoline and 10% alcohol. But recent comments from the Obama administration indicate that the EPA will provide a bailout to the corn ethanol industry, which will likely allow retailers to blend up to 15% ethanol into U.S. gasoline supplies.

The U.S. now has about 250 million motor vehicles. Of that number, only about 7.5 million are designed to burn gasoline containing more than 10% ethanol. And there is evidence that even that even 10% ethanol may be too much for the other 242.5 million. Last year, Toyota recalled more than 200,00 Lexus vehicles because of internal component corrosion that was caused by ethanol-blended fuel.

In addition to problems with their cars, consumers may soon find that more ethanol in their gasoline will result in the fouling of smaller engines. The Outdoor Power Equipment Institute, which represents companies that make lawnmowers, snowblowers, chainsaws and the like, opposes the bailout of the ethanol industry. It says that increasing the amount of ethanol in gasoline “could damage millions of forestry, lawn and garden, and other small engine products currently housed in consumers’ garages.”

The danger posed by ethanol-blended gasoline comes from the change in the fuel’s chemistry. Ethanol contains oxygen in its chemistry. Gasoline does not. Therefore when you use fuel with ethanol blended in, your engine will experience a leaner (higher oxygen content) mixture than if you burned pure gasoline. Modern autos are an exception. More on that in a minute.

Why should you care? Some of us remember when you had to fuss with the carburetor idle mixture screw to get your car to idle properly. The idea was to get the mixture neither too fuel rich, causing smoking exhaust, nor too lean, leading to rough idling or loping. Most gasoline-engine-powered equipment such as lawn mowers, snow blowers, leaf blowers, and similar machines still use carburetors. If your mower was built more than a few years ago, it was likely adjusted for pure gasoline (E0). Still, if it runs rough because your fuel now contains 10% ethanol (E10), you, or a repair shop, can probably adjust it to run acceptably.

Most gasoline engines run rich (excess fuel or reduced oxygen) when they are at full power (wide open throttle). This limits the peak temperatures of combustion and thus protects the (typically aluminum) pistons from overheating. If the air/fuel mixture goes leaner at full throttle, temperatures will rise. This is exactly what happens when fuel blended with ethanol is used. The more ethanol, the more oxygen and the hotter the combustion temperature. Is this the end of your worries with using ethanol bearing fuel in small gas engines? Not at all.

Ethanol has a strong affinity for water. If your engine’s fuel system is vented to the atmosphere, which is almost universal in gas engine powered machinery and boats, water can and will accumulate in the fuel tank. When the machine is cranked up after off-season storage, this water and related sludge may well make starting difficult or impossible. Further, older equipment can have fuel lines that are corroded by ethanol. For example, clear fuel lines help users see if fuel is flowing, but the manufacturer of Tygothane® clear states that the lines are “Not compatible with greater than 10% ethanol fuel.”

Anecdotal evidence shows that ethanol-blended fuel is already causing problems with outdoor power equipment. Discussions with small-engine repair shops show that ethanol-blended gasoline is causing problems. Steve Goodwin of the YardPro small engine repair shop near Clemson, SC and Richard Knox of Top Notch Marine of Seneca, SC both said that fuel system repairs have increased significantly since ethanol was made mandatory in most motor fuel. Goodwin has noted a 30% increase in carburetor gumming, starting about 3 years ago.

The bottom line is that 10% ethanol has caused a myriad of problems in boats, lawn and garden equipment, chain saws, and virtually all gas engine machines except modern automobiles. Increasing the amount of ethanol to 15% would be a real disaster for owners of such machines.

So how is it that modern cars are able to burn E10? There are three factors. First, since as far back as 1985, cars have been using oxygen sensor-controlled, feedback-adjusted fuel metering systems. In these vehicles, the mixture is maintained near stoichiometry (chemically correct) through sensing of excess oxygen or lack of it in the exhaust gas. Thus, the lean out effect of moderate amounts of ethanol can be compensated. Second, to prevent fuel vapor loss to the environment, all modern light vehicles use a vapor trapping system that also serves to prevent moisture entry to the fuel tank. Finally, the car manufacturers were aware of the planned use of ethanol and specified fuel system materials that could tolerate the corrosive effect of alcohol.

Here’s the punch line: The corn ethanol industry has used taxpayer subsidies to create capacity in excess of that required to put 10% ethanol in all of our gasoline. Now they are pushing for 15%. In other words, an excess of subsidies led the industry to build too many distilleries. Now the corn ethanol scammers have too much capacity. And the only solution for this excessive use of subsidies is, yes, more subsidies.

And the ethanol scammers’ plea for yet more subsidies is coming just as the Congressional Budget Office has determined that for each gallon of conventional gasoline that is displaced by corn ethanol, taxpayers are shelling out $1.78. Put another way, a barrel of crude oil on the spot market now costs $77. Using the CBO’s latest figures, replacing a barrel of gasoline with ethanol costs $74.76. And yet ethanol industry officials continue making bogus claims that they are saving money for taxpayers.

It’s time to put an end to the ethanol scam, the longest running robbery of taxpayers in US history. And Congress should do so before the scam is allowed to damage or ruin more lawnmowers, boats, and other equipment.

Harry Wertheimer, a retired automotive engineer, lives in Salem, South Carolina.