Diesel 10 is a large dark brown-olive warship diesel with a pale grey fierce-looking face, a cleft chin, danger stripes and a large robotic arm on his roof. Diesel 10 has had a few modifications throughout the television series. These include:

Calling All Engines!:
His pupils became bigger.
His brake pipe was removed.
The wipers on his front windows were removed.
His body is incorrectly fitted to his chassis at the front, leaving a gap above his front bufferbeam.
Misty Island Rescue:
The 'teeth