Car and Driver: Mileage? No, it's Your Gallonage that Really Counts

There's a sneaky illusion in mpg numbers. Consider: If your pickup rated at 10 mpg gets only 9, you shrug and say it's off only 1 mpg. But if you drive a hybrid labeled 50 mpg and it drops the same 10 percent to 45, you complain of lousy mileage.

The illusion tricks you once again when you think of mpg instead of the fuel you actually burn. Hybrids are chosen by people who think saving gas is right up there on the list of American virtues with motherhood and voting. But when the hybrid gets 45 mpg instead of the expected 50, a 100-mile trip consumes less than a quarter of a gallon more than expected. Compare that with the pickup that gets 9 mpg instead of 10; its 100-mile trip burns 1.1 extra gallons.

The loss of 10 percent on the pickup's mileage actually burns five times the extra gas used by the 10-percent shortfall in the hybrid...

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