As Chevrolet very often point outs in marketing its 2011 Volt extended-range electric car, more than 70 percent of U.S. vehicles cover less than 40 miles a day.

That means that if you recharge a Volt every night, and cover less than that distance daily, your car might never, ever need to switch on its range-extending gasoline engine to generate electricity.

Which leads to a whole host of questions carmakers have never had to consider: Will the engine run right if it's never started? Will the gasoline get stale? And so forth.

The answer is something called "maintenance mode," in which the Volt decides its engine needs to be switched on to circulate the gasoline, warm up the system, and otherwise run for a while to keep everything in good operating order.

2011 Chevrolet Volt on test in Little Rock, Arkansas, July 2011

2011 Chevrolet Volt on test in Little Rock, Arkansas, July 2011

The video below shows the maintenance mode screen on a Volt belonging to Andy Oury. He's a battery systems engineer at General Motors whose commute is short enough that his car almost never has to switch on its engine.

Maintenance mode for the Volt's 1.4-liter four-cylinder engine took about two minutes, Oury said, and consumed roughly one-tenth of a gallon of gas.

As of the video, posted Monday, Oury had covered 1,554 miles, almost all of it on grid power from recharging his battery pack at night.

Over that distance, his car has burned about half a gallon of gasoline, making its effective gas mileage a whopping 3,000 mpg.

The Volt's display, however, tops out at "250+ mpg," removing an incentive for Volt owners to compare truly ridiculous gas-mileage numbers.

Too bad.



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