A development mule is an early-stage engineering testbed vehicle. Automakers use mules to test new engines, drivetrains, or suspension systems in real-world conditions before the final body design is ready. Mules are often cobbled together using the modified body shell of an existing production car to hide the prototype components from spy photographers and competitors.
Heard on the job
We spotted a development mule doing hot weather testing in Death Valley, wearing a modified current-gen body but sitting three inches wider.
Also heard as
- mule
- test mule