Please stop giving people ideas....

Anyway, ideas are far more dangerous than the people who would use them... <sarcasm

If the sugar becomes solvent with the gas it will crystalize when it hits the injectors (high speed jet in a carb) effectively killing the "normal" operation of the vehicle by clogging the indectors.

IF it becomes solvent with the gasoline.

As for the $8,000 repair, there are vehicles out there (say a Mercedes ML55 AMG) that has a hand built engine (only 2000 of them made in the year 2000) that are very expensive and add that to the dropping of the tank and you could exceed $8,000.

Would you prefer the sugar or the potato? Or, both for good measure?

How about just stealing the gas cap? Doesn't the gas cap have to be on for modern cars with all the fuel emission stuff to function?

No, leaving the gas cap off throws a light on the dashboard. That is if the owner hasn't covered it with electrical tape already.

Didn't Mythbusters do a segment on this that gasoline does not dissolve sugar?
http://mythbustersresults.com/episode15

Bleach on the other hand didn't screw up the engine, but did rust the gas tank (bleach is an oxydizer), but assuming that it's a metal tank in a modern car is a bad assumption.

Objects in the exhaust are ejected, however, if you can jam it up really good, it will eventually stall the engine. To destroy it, you'd have to find that just right setting between totally free and totally plugged up to burn the exhaust valves. Kinda hard to do on purpose.

This guy was taken for a ride, or the police were taken for a ride.