How much a $1.5 million car that raced in the Indy 500 would be worth had it won

On Thursday's episode of CNBC's "Jay Leno's Garage," renowned auto appraiser Donald Osborne explains to host Jay Leno how three classic 20th century race cars have appreciated in value just over the past five years.

As Osborne notes, "Everything old is new again." This comes in response to Leno's joke about Osborne's throwback purple pants. But the wisdom applies to cars as well.

With its two-speed transmission, Offenhauser racing engine and wheels ready for dirt or asphalt, Osborne calls the Midget the "fundamental racer." It originally went for $7,000.

Its heyday was known as a time "when the sex was safe and the driving dangerous," Osborne says. It was not uncommon for drivers to veer off the race tracks and flip the car, which did not have a protective roll bar, and end up with a neck injury.

Drivers call this Chevy, which was popularized by the eponymous Beach Boys hit, "the 409" on account of its 409 cubic-inch size and 409 horsepower engine.

At an MSRP of $2,800, this was originally purchased by a 17-year-old drag racer Butch Leal, who took out its turn signals, radio and other interior elements to optimize its performance on the track.

It still has its original, raggedy interior, but don't let that fool you. This car has appreciated a lot.

Named after an "absolute legend," Indy 500 racer Dan Gurney, these turbo-powered cars have engines with anywhere from 600 to 1000 horsepower.

This one originally sold for $35,000 and is now worth $1.5 million. According to Osborne, if it had actually won the Indy 500, it would be worth about five times that.

As for how much it and the others have appreciated in just the past five years, watch the video to find out.

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CNBC's "Jay Leno's Garage" airs Thursdays at 10 p.m. EDT.

Video by Richard Washington