Just for kicks, I wanted to ask Fuelly-at-large about fuel additives (lucas, techron, stp, acetone, ca40g, whatever...)
Does anybody use' em, have any made a difference, etcetera, etcetera. Given the nature of this website as a recordkeeping tool, I'd love to know: has anyone run any experiments, and would you care to share your results?
I've mainly used Lucas Fuel Treatment (2-4oz per fill-up) and almost every STP product useable for my car.
I don't expect to see a big difference in the short term since my car is fairly new (2007 Toyota Matrix w/ 60xxx km) but I know it protects and cleans my engine and fuel system to keep my car from breaking down in the long run.
I do not run anything over recommended octane rating because it makes the engine and ECU think different that what your car is actually needing. (in simple words)
In my experience modern gasolines are fairly clean, calling oneself a detergent gasoline is basically redundant since gasoline is a solvent in and of itself. That being said before I take my cars in for their smog checks I tend to run a tank with a name brand high quality fuel injector cleaner through them at least 2 or 3 tank fill ups before taking them down for the test, I figure it may be wasted money but it probably can't hurt.
I would steer clear from anything containing acetone, it is a very polar solvent and can damage hoses, gaskets, and seals in your engine and fuel system. Acetone also has a propensity to hold water similar to that of alcohol and water in your fuel system is not good ever. It is bad enough that we have to use ethanol fuels that attract and hold water, but I wouldn't consider adding an additional water attractant to my fuel. A tiny flake of rust can wreck havoc on your fuel pump or fuel injection pump if it wedges or lands in the wrong place.
I agree completely with MatrixDom, don't add octane if it isn't needed for your application, it will cost you money with no return on investment. If your engine is suffering from detonation, knocking or pinging, go the the next higher pump octane rating for a few pennies a gallon but don't pop for a bottle of Octane 105 at $5.00 a fill up, your car will run best on the lowest possible octane rating that prevents detonation, higher octane ratings than that figure are just wasted money.
Since the Department of Defense does not authorize fuel additives (except a specialized one for jet aircraft) on the grounds that they do nothing productive, I do not use them. I have used Sta-Bil for winter storage, but cannot tell that it made any difference.
About a year ago I started adding the tag "E-10" whenever I bought fuel that I know actually is E-10. Many places have the pumps flagged with something like "May contain up to 10% ethanol" which isn't very helpful. And I understand some States do not require pumps to be labelled. I have not been able to detect any difference in milage with E-10, either in my cars or my motorcycles.
I drive a diesel and I'm not happy about the fuel consumption. I've seen many diesel fuel additives that claim to give more power and better fuel consumption. Most of them are some sort of fuel injector cleaner, some are anti gelling which I think happens in colder climates but I live in a tropical country where the quality of fuel is pretty crap (up to Euro2 standards only). Are diesel fuel additives affective or just a bunch of marketing bull??
The only additive I use is a Fuel Injector Cleaner (Wynns). Other than that, I steer very clean of any fuel that contains Ethanol. Every time I use E-10, I lose 20% mileage (my car REALLY hates Ethanol).