steve, a diesel engine can run on amixture of fuel[petrol/deisel
but the mix has to be more diesel than petrol so if your wife hasnt filled the car up to the top just refuel with diesel the car wont run very well for a while but it will run alternatively, and this is the correct way drain off all the contaminated fuel mixture and change the fuel filter and top up with correct fuel
[we used to use petrol in our diesel when driving in severely cold weather below zero the petrol would stop the diesel from waxing up causing the diesl engines to stop running, anyway
good luck m8
alanmellor, June 2006