There was a ahow,on TV here they took vehicles across the tundra on an extreme race, and one got a bunch of grass up around the manifold or whatever, and it dried it out and caught fire. They caught it In Time, and was easy to put out. Luckily it did fubar the whole,vehicle. But Hat is extreme conditions and driving to be sure.
a few years ago a florida highway patrol car caught on fire after the trooper kept it running in tall dry grass on the side of a highway...
catalytic converters get extremely hot and are known for starting fires...