With gas prices high, you'd expect people to buckle down and hang onto their existing cars rather than spending the money to buy new ones, right?

Errrrrrr, actually not.

According to Mike Jackson, the outspoken and always quotable CEO of AutoNation, buyers who've put off their new-car purchases are now returning to dealers. And at least some of them do so precisely because new-car gas mileage is now so much better than what they're driving today.

It's a confluence of two events: The mandated fuel efficiency of new cars in 2012 is higher than it's ever been (it will increase steadily through 2016), and as the economy slowly recovers, consumers increasingly need to replace cars that are older than they've been in 60 years.

The average car on U.S. roads is now more than 10 years old, the highest age since World War II ended U.S. auto production entirely for four years.

With more reliable cars that require less frequent servicing, the nation's muffler and transmission shops report booming business as drivers spend just enough to get one or two more years out of their old cars.

But with the economy improving, new-car sales are slowly returning to their historic levels. Part of that, Jackson told Bloomberg, comes from consumer desire for more efficient vehicles.

Auto loan

Auto loan

AutoNation is the country's largest chain of new-car dealerships, so Jackson's comments come from reported consumer behavior reflected in actual car sales.

Jackson didn't supply data teasing out what percentage of consumers bought a new car to improve their fuel efficiency who otherwise would not have done so, and it's likely a mix of motivations that's getting people into dealerships.

But a survey by researcher J.D. Power & Associates earlier this year indicated that fuel efficiency has passed reliability, price, and styling to become the most influential reason for the purchase of a new car.

"It’s really astounding that you’ve gone from $4-a-gallon gasoline devastating sales" in 2008, Jackson said, "to $4-a-gallon gasoline supporting sales today."

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