Tesla's electric car is a confession of his supposed nephew Peter Savo, which he told Derek Ahres on September 16, 1967. In that confession he claims that Tesla took him to Buffalo, New York in 1931 where he found a modified Pierce-Arrow car.
As explained, Tesla modified the car by removing the gasoline engine and replacing it with a brushless AC electric motor. The engine was powered by a "cosmic energy power receiver" placed in a box about 25 inches long, 10 inches wide, and 6 inches high, which consisted of 12 radio vacuum tubes and was connected to a 6-foot-long (1.8 m) antenna. According to statements, it was said that the car was tested for 8 days during which it was driven 50 miles at speeds of up to 90 mph.
Source: Visual available in Nikola Tesla Legend website store https://store.nikolateslalegend.com/en/?v=fd4c638da5f8
Although no physical evidence has ever been found that the car actually existed, and considering that Tesla never had a nephew named Peter Savo, the story was declared fictional. Also, it caused many debates due to the fact that Tesla invented the car's propulsion system.
As reported by John J. A. O'Neill (Science Editor of the Eagle) on July 10, 1932 - „Famed Scientist, on Eve of 76th Birthday, Says He Has Succeeded in Harnessing 'Penetrating Rays' to Operate Small Motive Device“
According to his report, Tesla made the following statements:
"The attractive features of the Cosmic rays is their constancy. They shower down on us throughout the whole 24 hours, and if a plant is developed to use their power it will not require devices for storing energy as would be necessary with devices using wind, tide or sunlight."
"All of my investigations seem to point to the conclusion that they are small particles, each carrying so small a charge that we are justified in calling them neutrons. They move with great velocity, exceeding that of light.
"More than 25 years ago I began my efforts to harness the cosmic rays and I can now state that I have succeeded in operating a motive device by means of them."
"I will tell you in the most general way," he said. "The cosmic ray ionizes the air, setting free many charges—ions and electrons. These charges are captured in a condenser which is made to discharge through the circuit of the motor."
"I have hopes of building my motor on a large scale, but circumstances have not been favorable to carrying out my plan."