[paul.fr]

A prank we used to play on mischievous night, was to pour sugar in a cars petrol tank. What actually happens when you do this?

[moonfire]

You will not be able to drive as it goes through the petro lines....I know...it happened to me and I did not turn my car on...instead, we took the gas tank off and went to a car wash and power washed it after emptying the gas out of it....then took a sprayer and filled it with alcohol to dry out the gas tank.  I had my lines checked and because I did not turn it on, the lines were free and clear of the crystalized mess.  I was able to drive my car with no problems after it was put back together again.

[ukmicky]

Mythbuster did a program on puting stuff like that in the petrol and found as long as you didnt go mad with the ammount you mix in that most cars will continue to run with almost anything mixed in.

i love mythbusters.

[JimBob]

Yes Micky,

A.) I agree B.) I can attest to this.

In my misspent youth, all us guys tried this with each others cars and none of us ever had to clean out our gas tanks. I once put a pound of suger in a car belonging to a friend of mine and it never missed a stroke. Of course, I suspect the engine of a '49 Plymouth could run with bullets inserted every other stoke into the pistons!

[moonfire]

Really?  Now that is interesting as I had a girlfriend who had it done to her too and she drove it not too far and it stopped running.  Of course, it was a Datsun and I had a little 1993 Dodge Ram Pickup(with a mitsibishi engine) I didn't want to take any chances on it....

[another_someone]

On modern cars, at very least, I would have thought it would damage the oxygen sensors, the cat, and and maybe the injectors (not that I have tried).

[paul.fr]

On modern cars, at very least, I would have thought it would damage the oxygen sensors, the cat, and and maybe the injectors (not that I have tried).

yet!

[Bored chemist]

Since sugar doesn't dissolve in petrol it won't have any effect except that it bungs up the pipes and filters. The oxygen sensores and catalyst are pretty much safe.
I once spoke to the guy who did the research on this during WWII. The needed to be able to render any fuel useless because (in a quick retreat) they might not have been able to take it with them. They concluded that sugar was totally useless- all the enemy had to do was wait for it to settle out and pour off the petrol. They did come to some conclusions about what would work but, lets say "I don't remember" what they used.