Electric cars are not only the cleanest cars in the world, they're some of the fastest, as quite a few Tesla Model S owners have demonstrated racing against various gas cars on drag strips.

Even manufacturers of internal-combustion cars apparently know this. In a recent Twitter ad for the Challenger Demon, Dodge called it "The world's fastest 0-100-mph production car."

Then, however, Dodge added a surprising disclaimer: "Excludes non-mass-production vehicles." Fair enough, the 840-horsepower Challenger may not be as fast as a 1,479-horsepower Bugatti Chiron.

And then the disclaimer got more surprising by adding, "...and hybrids/electric."

In other words, Dodge acknowledges its purpose-built drag-racer has been unable to beat numerous Tesla Model S P100Ds. For the ad's target audience, who may spend $85,000 for the ultimate drag-strip bragging rights, the ad might as well say, "nevermind, just go buy an electric car."

This ad is from the same company, Fiat Chrysler, that builds the electric Fiat 500e, of which CEO Sergio Marchionne said, "I hope you don't buy it, because every time I sell one it costs me $14,000."

Wiebe Wakker, who is driving a VW Jetta wagon converted to electric power from his home in Holland to Australia, retweeted the ad, noting the irony.

Perhaps the bigger irony is that the disclaimers might not even be necessary for accuracy. In drag races between the 840-horsepower Demon and the 762-hp Model S P100D, the Tesla blasts away from the Demon from a start, but the Demon reportedly reaches 100 mph about a second sooner than the Tesla.

Since automakers are reportedly not airing as many ads for electric cars as they do for other cars, it's interesting to see one promote electric cars in ads for their complete opposite from an environmental standpoint.