Putting diesel in a petrol car is a bad idea. The car will travel for about 1/2km as it uses up the the petrol in the carburetor. Increasingly pinking then eventually giving up the ghost with black smoke billowing out of the exhaust. On older cars this is not a disaster. Simply draining the diesel out of the fuel tank, refilling with petrol and then then clearing its throat for about 10 minutes can cure things.
The research for this node was carried out by my stupid boyfriend on a hire car in Cyprus. The car sounded like a diesel and the filler cap gave no indication as such. Diesel does however have a distinctive smell so sniff the tank if you are not sure. Also, UK filling stations have nozzles of a different size for petrol and diesel to prevent such accidents.
As it turns out we were not stranded for long as we were soon picked up by the Greek Police, being as we were on the edge of no-man's land on the Greek/Turkish Cypriot border.