what fuel additive?

Why don't you try it on yours, and let us know how it goes.

Well, there's no fuel in fuel additives. That's why it is an additive. It is meant to be "added to" fuel. 

Basically, you'd be pumping a concoction of detergents through the fuel lines and into the motor. It isn't my idea of a good time considering the damage not just possible, but likely to occur to the fuel injectors, fuel filter, fuel pump, motor, catalytic converter.....and depending on the additive, it may not start, it may clog up your lines, it may eat through the lines.....

I'm not seeing a scenario where this is a good thing to attempt at all. While I appreciate your question as I too often have wild thoughts like that myself, I'm comfortable with saying you really don't want to dump a bunch of crap in your fuel tank and then try to run it through your fuel system. Fuel systems these days are pretty complex, and I think it is a very bad idea.

It likely won't run. Read the labels, if it says it's flammable, it may, if not, then it won't. It wouldn't really be worth trying in your car, to get enough in the tank for the fuel system to pick up more than gas would be way too expensive. Try a lawn mower if you really want to know. At least that will be easy to clean out. 

@mountainmanjoe Ehh I have enough problems with my 07 Chevy avalanche.. Heh, heh, I’ll buy a cheep beater to do that with.

I am thinking of using a fuel-additive for my car on the next road-trip from Seattle to SF.
Is it a bad idea to use fuel additives in such a situation ? I feel the continuous high speed driving would help even more so.

2007 Highlander V6 3.3 104K miles.