I don't think the bottle additives offer anything over what the detergents already in the pump gas offer.

Fuel injector cleaner and stuff like that usually just boosts the octane up a bit more..

There is certain engine cleaners you can use that are either put inline of the fuel system usually just before the fuel rails and are a machine then there are ones that are injected into your engine through a vaccum line those actually work the one we use at work is called Top Engine cleaner, they really work cause when you use them they spit tons of smoke(carbon mostly) out the tail pipe.

Ignore the injector cleaners/fuel system cleaners. They really don't make any noticable difference, but if they do, you have other problems.

The Top End cleaner that T-bird mentioned is definetly worth it. By knocking out the carbon from the engine, it opens up the intake, smoothes out the incoming air and prevents the fuel from getting soaked up by the deposits.

my economy improved 18% when i did that... paid itself off in 1 week :)

Any brands of top end cleaner you guys would recommend? I've never done it to my engine, so I should probably try it.

its actually not just cleaning material... but a process of removing carbon scoring on the intake manifold; while the engine is running... valvoline is where i have the fluids i'd rather not change myself done :-p

Go to a GM dealer and in the parts department look for a bottle of GM Top End Cleaner.

the instructions should be on the bottle.

no they don't really work. i tried it on a really old car and didn't notice any diff in economy except my engine ran really rough whilst on the stuff.

cool, thanx man :)

the only thing that i know works is Engine Restore. But the engine needs to be in a weaker state/high milage to notice. But it does wonders. I have also used Z-Max addivitive b/c i was running a bit rough. that smoothed out my idle and gave me a 1-2 mpg increase. but the others are pretty much junk, they do work just not what the bottle says.

i sell the kits and chemicals to do this stuff, and the basic kit is about 100 bucks, a nice kit that can interface with the fuel rail to clean injectors is like 280 bucks lol

periodically, we've been wondering about that 10th AE miata... ;) hows' she doing?

holy crap I paid like 15 bucks for the Top End cleaner from my parts department, And at school it was about 20 for a bottle to use on the fuel rail style machine.

The 'fuel system' cleaner solvents you can buy can seriously degrade the seals in the fuel injectors and other components with some manufacturers! Alsa, as is the case with my car, the throttle body is plastic and has a sealent layer on its surface, one person used the 'top end cleaner' and it took this layer off, and reduced the tolerences of the fit of the butterfly in the throttle body screwing his idle!
I tend to stay away from such things, especially in modern cars, it doesnt tend to agree with your lambda sensors either :?