One appliance and crew from Hillingdon, one from Gerrards Cross and one from Langley attended.
One car was fully alight on the hard shoulder of the slip road, when they arrived.
The firefighters used one set of breathing apparatus and one hose reel.
The motorway slip road was closed while they worked at the scene.
The car was destroyed by the fire.
Thames Valley Police and National Highways also attended.
