Dear Car Talk:

If you drive one of the new plug-in hybrids or a gas/electric hybrid on pure electric for an extended period — say, six months or so — is it possible for the gasoline in said hybrid to go "bad"? I'm guessing not, that the movement of the car would keep the fuel mixed and not let it separate (or whatever happens to old fuel). Thanks! — Ed

Theoretically, the gasoline can go bad. Condensation can build up in the gas tank, and if gasoline sits long enough, it can break down and create varnishes, which can clog fuel injectors.

But manufacturers have anticipated the problem. In the Chevy Volt, for instance, if you've been driving on nothing but electric power for six weeks, the car will go into maintenance mode and run the engine for a short period of time. That removes vapors and condensation, and keeps the engine lubricated.

If you manage to go a whole year without using the gasoline engine, the engine will automatically run until the tank is empty — or until you refill it with fresh gas.

Toyota has a similar system for its plug-in hybrids.

Bottom line: Don't worry; be happy, Ed.

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