Are we talking utter destruction or something that could be fixed for say, $400?
cost of fixing it depends on how much you put in. possible damages include but arent limitied to in order of what gets damaged first:
fuel pump, filter and lines
fuel injectors/carb
at this point the sugar is hot enough to carmelize the engine
heads/valvetrain
piston and crank damage due to the less compressible and combustible nature of caramel
exhaust valves/heads
this doesnt include incidental damage cause by an engine that runs poorly.
485 posts and you don’t search the archives… tsk…tsk… 
Been done by the bigfella:
http://www.straightdope.com/mailbag/msugargs.html
and
http://www.straightdope.com/mailbag/msugar2.html
Cool, my first simulpost!
You’re not contemplating doing this to someone for revenge, are you?
No, it’s actually the other way around. On another message board that I frequented, on of the posters got in a hissy fit because I called him out on a couiple of things and as a result he has made at least 3 “threats”/mentions of putting sugar in my gas tank.
The bozo in question lives in the Boston area, and thanks to another asshole on the same message board, Dickface #1 has my home address, and it wouldn’t be too much trouble for him to drive up to Bath, ME.
But that’s why I always keep an aluminum bat handy.
I’d recommend a locking gas cap. The baseball bat might lead to legal hassles, to say the least. Also, the bat only works in you catch him in the act.
Speaking of catching him, can you rig a video camera to record your car while you sleep? Wouldn’t it be great to have hard evidence to turn over to the cops?
An ex-coworker of mine did this and caught the a guy taking a baseball bat to his 2 year old mercedes on tape. He he called the police, who came out and took a report, were of minimal assistance. His INSURANCE COMPANY OTOH was apparently a joy to watch in action. They promtly filed suit against the indiviual in question and IIRC eventually got his wages attached to pay back something like $4,800 in damage.
will the person who owns the car know that it has been hit with sugar ? how much sugar will it take to do major engine damage ? 10 lbs. ? 20 lbs. ?
ETA
Beware: zombie thread. Sweet, sweet zombie thread.
From the first Dogster SDSAB cite provided above:
From the second cite:
The damage a 10 or a 20 pound bag of sugar would do would also depend on the height dropped from and where it hit.
Pretty sure I read Cecil’s column about this. Neatest thing I remembered learning about it is that sugar has no real chemical interaction with the fuel & fuel system. It just clogs it up like sand would (sugar doesn’t dissolve in gasoline). Sugar’s just used because most everyone has a bag of it in their kitchen (as opposed to having a bag of sand)…
I agree that sugar does not dissolve in gasoline. Years ago, I experimented by adding sugar to a small vial of gas and after three weeks it had not dissolved. This was a follow-up to an insurance claim alleging sugar had been added to gas resulting in complete engine failure of an outboard marine engine. Gas samples were analyzed by a laboratory revealing no dissolved sugar. Naturally, the design of the fuel system of an auto may allow particles of sugar to contaminate the fuel system.
Later it was determine the actual cause of the engine failure was due to the owner neglecting to add motor oil to the engine’s gasoline resulting in overheating and failure.
My dad told me the (apocryphal?) story of resistance types doing this to German trucks (along with the warning “If I evr hear of you trying this, you’re in big big trouble!”). Allegedly it got into the cylinders and burned to a sticky mess making the engine seize up.
Of course, this was in the days of fuel-inefficient carburetors, and I wonder what 1930’s/1940’s era vehicles did for fuel filtering and how fine the carburetor and choke jets were?
Sugar does not dissolve in gasoline, but it does dissolve in alcohol and in water. Gasoline combined with alcohol is common in some parts of the country, and while water in the gas is not terribly common it does occur occasionally. If the sugar is dissolved it will generally form sticky deposits in time that can clog fuel injectors, and in some cases can affect interior engine parts. Repair costs can range from zero (small amount of granular sugar that never dissolves) to hundreds (clean out gas tank, clean or replace fuel system parts) or occasionally thousands (clean tank and replace remainder of fuel system, overhaul or replace engine).