We think it’s safe to say that most of you reading this article right now can remember a time when gasoline was at or under $1.00 a gallon…and frankly, it wasn’t all that long ago. Today, a gallon of premium fuel (required for many modern high-performance cars) runs close to $4.00 a gallon, meaning every outing in a classic car like a ‘66 Ford Mustang is costly. While you can’t put a price on “smiles per gallon”, many Americans still have to think twice before turning the key on their classic car for a Sunday cruise.

Wouldn’t it be nice if there were a cheaper alternative to gasoline that didn’t ruin engines or performance? Well there is, and it’s called propane. You know, that stuff you grill or heat your camper with? Well one So Cal Mustang fan performance a propane conversion on his ‘69 Mustang coupe to power a turbocharged six-cylinder engine. This is one weirdly efficient Mustang that doesn’t lack for power, and for $15,000, it can be yours.

Jalopnik was tipped off to this So Cal craigslist find, and given the California context, the propane conversion makes even more sense. A propane conversion to a carbureted car only costs about $1,000 before you factor in the fuel tank (which can cost $1,000 by itself), and propane autogas typically goes for about $1.99 a gallon. While you may seem a slight drop off in performance, propane is a much cleaner fuel, both in emissions and in engine gunk. Generally, you only have to change the oil in a propane-powered car every 10,000 miles. That’s how clean it is.

Of course all this don’t mean squat if your ‘69 Mustang accelerates like a Prius, and we’re thankful the owner thought to add a newer turbo to the 200 cubic-inch inline-six under the hood. While it still doesn’t make small-block V8 power, it would be plenty of fun to drive, especially with the new suspension and three-speed manual transmission. Still, $15,000 is a lot of money to “pony up” for this weird, one-of-a-kind muscle car, and if you like kinda out-there cars, this cleaner-burning, turbo-six Mustang might not be for you.