The 1964 Panhard LM64.

By most accounts, Le Mans is the world's most prestigious sports car race.
Held in Le Mans, France, every year since 1923, it's certainly the oldest active endurance race. Roughly 60 of the world's fastest cars race for 24 hours along the serpentine 13.67km Circuit de la Sarthe road course.

Back in the 1960s, the race was very different. Speed wasn't the only focal point. The second most valuable award, the Index of Efficiency. It focused on a car's speed, weight, fuel consumption, and gas mileage at racing speeds. It also looked at the vehicle's drag coefficient (Cd), an aerodynamic measurement of how a car slices through the air.

So what business does a pair of diminutive, mild-mannered 78hp - gorgeously designed and supercharged – Panhard LM64s have racing on a track with Ferrari, Porsche, and Ford GT40s?

In 1959, Le Mans began giving awards for the Index of Efficiency. Some believe it may have been partly due to the Suez Canal Crisis that occurred a few years earlier and highlighted just how easily the flow of petroleum could be disrupted to Western Europe.

The winner was a Panhard, sporting a 744cc engine and posting an 9.16L per 100km. In business for almost 25 years, the company was helmed by French automobile designer Charles Deutsch and engineer René Bonnet. It was widely known for building super lightweight, ultra-aerodynamic sports cars.

Unfortunately, Deutsch and Bonnet disagreed on how future cars should be designed. Not only did they clash on engine types — Deutsch wanted to stick with Panhards, but Bonnet wanted to go with Renault.

So, in 1964, using the Panhard chassis as a base, Deutsch and his team went about creating a pair of bespoke racers (LM64-01 and LM64-02) powered by an 848cc engine with the intention of winning the Index of Efficiency trophy. Everything was designed to eliminate drag.

The most noticeable design choice was the sleek, "slippery," elongated, almost dolphin-like body, with spats enclosing all four wheels. The bellies of each car were fitted with a wholly encased underbody that helped generate downforce and glue the car to the road, a concept later called ground effect and not widely used for a few more years. The high-reaching dual fins (very dolphin-like indeed) on the back helped cut a clean line through the wind. Front headlights on the rounded bulbous nose were also fully enclosed.

Deutsch tested the airflow of the LM64 body at the Gustave Eiffel Aerodynamic Laboratory. If Gustave Eiffel sounds familiar, he's the guy who built the famous tower. Interestingly enough, he also made the lab in 1912, and since it's still operating, it is considered the world's oldest aerodynamic test lab.

The 848 cc engine wasn't powerful under Le Mans regulations, so they attached a Sferma supercharger, which boosted it to an "official" 1.18L, allowing them to run in the under 1.2L class.

Both cars entered the '64 Le Mans, but neither car finished. Ferraris took the top three spots (and five of the top six), and Porsche took five of the next six. The Panhard CD LM64-01 ran for 13 hours (124 laps) before gearbox problems halted its race, while the LM64-02 ran for 10 hours (77 laps) before its engine failed.

Neither car raced again until both took part in the 2004 Le Mans Classic during the 40th anniversary of their only race. Panhard was taken over and merged into Citroen in 1967.

Today, the Panhard CD LM64 is regarded as one of the most recognizable prototypes ever to race at Le Mans and the most aerodynamic car of all time.

With a coefficient of drag of just 0.12, it's sleeker than every automobile ever made, including the McLaren Speedtail (Cd 0.278) and every Tesla model.