Car Talk

March 2006

Dear Tom and Ray:

Last May, I graduated from Johns Hopkins University with a degree in biophysics. Being a poor graduate student (and a cheapskate, to boot), I was wondering if there is any way I can use my chemistry knowledge to increase my gas mileage? In college, a chemical engineer named Mike and I created a super still in the back room of his house. I provided genetically engineered yeast that had its methanol-producing gene knocked out, and he designed the rig. I own a '95 Toyota Camry. My question: How much ethanol/methanol can I add to each tank of gas without destroying the engine? Is there any simple alteration I can make to my car that would allow me to increase the alcohol-to-gas ratio? Lastly and least importantly, is this legal? -- David

RAY: Well, I don't know anything about the legality of backyard stills, David. That was all my brother's idea -- I swear!

Beat up old car

TOM: I actually don't know anything about the legality of your home biochemistry lab, but there's nothing illegal about using a mix of gasoline and ethanol in your car. It's done all the time.

RAY: Ethanol has long been seen as a potential replacement for, or supplement to, gasoline. Since it's produced from plants -- like corn -- that grow prolifically in the United States, acquiring a steady supply of the stuff doesn't require invading any Middle Eastern countries. Which is a definite plus.

TOM: For a couple of decades now, some gasolines have been successfully mixed with ethanol. They're normally found in concentrations of 5 percent to 10 percent ethanol. In the early days, there were some problems with these "gasohol" fuels, because the alcohol degraded rubber hoses and seals in fuel systems. But that seems to be a thing of the past, at least in these low concentrations.

RAY: So you're probably safe adding 10 percent ethanol to your car without having any problems.

TOM: Now, when you ignore our advice and ruin your '95 Camry with a mixture that's 50 percent ethanol, you should make your next new car a "flexible-fuel vehicle." Flexible-fuel vehicles are designed to run on almost anything; gasoline, ethanol, flat ginger ale, hummus.

RAY: Actually, they can run on ethanol, gasoline or any blend of the two. But they're really designed to run on something called E85, which is 85 percent ethanol and 15 percent gasoline.

TOM: They could, theoretically, run on 100 percent ethanol. But by adding 15 percent gasoline to the mixture, you help the car start reliably, since gasoline is more volatile and is easier to get started.

RAY: It appears that flex-fuel vehicles are about to get more popular. Ford and GM are the leaders in making flex-fuel cars and trucks, and they're getting ready to push the technology. There are actually hundreds of thousands of flex-fuel vehicles already on the roads. But most of them are running on gasoline only, because the owners can't find enough gas stations that sell E85 yet.

TOM: Of course, that won't be a problem for you, David. While I suspect you're going to have to move your little still to a bona fide laboratory in order to comply with local zoning and fire codes, with a flex-fuel car you'll be in fat city, man. And what you don't burn, you can use to make after-dinner drinks.

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