Development mule

Porsche 918 Spyder development mule in Monaco

Two Nissan GT-R "Black Mask" test mules on a truck in Japan

A BMW near Munich in October 2013

A development mule or a test mule in the automotive industry is a testbed vehicle equipped with experimental or prototype components for evaluation. Automakers evaluate aspects of vehicles before a full pre-production car is built to find problems. Mule cars are drivable, often years ahead of actual production. They may come after concept cars that sometimes lack critical mechanical components. They may also have advanced chassis and powertrain designs from a future vehicle that need to be tested, but "clothed with the body and interior of some other car about the same size."

Engineering mules are often heavily altered current production vehicles or disguised as completely different models. Mules may also be based on another manufacturer's model if no comparable model is available in-house or if an external benchmark is being used. For example, in the 1970s the first-generation Ford Fiesta was developed using mules based on the Fiat 127 (a car considered the class leader of the period), as Ford had no comparable compact model of similar size at the time.

Some noticeable alterations include simple cylindric shapes for the lamps in the taillights, different rims on the front and back without centrecaps, and a severe amount of added plastic and tape to hide the actual shape and design of the vehicle.

Development mules are most often used very heavily during testing and are scrapped. In unusual cases, test mules were acquired by members of the automaker's engineering team.

See also

• Automotive design
• Pre-production car
• Vehicle glider