Back to the Future film trilogy, the time machine is built from a DeLorean DMC-12sports car, and its appearance and features change in each movie. While it is the same car, it is seen in three different states throughout the films.

Back to the Future 
The original time machine is powered by plutonium, which generates the required 1.21 gigawatts of electricity to power the flux capacitor, and it must reach 88 mph to travel through time. The car has a license plate that reads "OUTATIME". 

Back to the Future Part II 
After Doc Brown's trip to 2015, the DeLorean is upgraded with a "Mr. Fusion Home Energy Reactor," which allows it to generate the necessary power from household garbage instead of plutonium. The car is also converted to fly, with its wheels folding for "hover mode," and the license plate is replaced with a barcode.

Back to the Future Part III 
After being struck by lightning and sent to 1885, the DeLorean's time circuits are damaged, and it is left unable to travel under its own power due to a damaged fuel line. Doc Brown and Marty McFly must use a steam locomotive to push the car to 88 mph on a railroad track to send Marty back to 1985. For this, the car's tires are replaced with a set of steel train wheels.