NEWPORT NEWS, Va. - Nine years ago, Jeff Caplan was working on a 1980 five-series BMW and needed to fix the odometer. "Every speedometer shop I contacted said the same thing, 'You have to send it in.

If you've ever modified a car with smaller or larger tires or, perhaps, a different final-drive gear, you've immediately screwed up your speedometer. This is, of course, annoying, but for modern cars ...

LITTLETON, Colo. — The U.S. Justice Department calls it “clocking”: intentionally rolling back an odometer to make a vehicle appear less used. Odometer rollback is “the single most common fraudulent ...