My acetone results

[Big time]

I tried acetone back in 2008 or so when fuel was pricey.

It gave more low end (idle) torque to the point where I didn't even had to push the gas pedal at all for rush hour traffic. (It was on a manual transmission car, and I only needed to shift gear and slowly release the clutch pedal to move the car a few feet).
I did some tests and it appeared to improve mpg a bit but rush hour traffic is impossible to compare accurately as it is never the same everyday.

Reportedly it allows fuel to vaporize much better by reducing surface tension.
Surface tension - Wikipedia, the free encyclopedia
Acetone In Fuel Said to Increase Mileage

You have to use very little of it as too much can actually hinder fuel economy.
The Mythbusters used too much and got no better mpg.
I used a medical syringe without the needle as you only had to measure a few cc's every time you pump gas.
I don't remember the exact amount but I believe it was UP TO 2 cc's for every gallon. Do NOT use any more than that.

IMO fuel economy can be improved only if your driving habits allow you to use the higher torque at lower rpms.
For highway driving it might increase mpg only as long as you are able to drive at lower rpms at higher gear.

Anecdotal experiences suggest that it works better on older cars where the computer or Oxygen sensor doesn't fine tune the fuel mixture so much.

[Christ]

I just would love to point out here that in almost any car, you can slowly release the clutch without feathering, or touching at all, the accelerator.

In fact, if I'm ever in a car in which I /can't/ do this, I consider it a fault worthy of diagnosis and begin working on it.

You should be able to start in 1st or 2nd and run it up to it's highest gear on flat, level ground without ever touching the accelerator.

[GearheadTool]

Originally Posted by Christ

I just would love to point out here that in almost any car, you can slowly release the clutch without feathering, or touching at all, the accelerator.

In fact, if I'm ever in a car in which I /can't/ do this, I consider it a fault worthy of diagnosis and begin working on it.

You should be able to start in 1st or 2nd and run it up to it's highest gear on flat, level ground without ever touching the accelerator.

I do apologize for the older thread bump but I had an older I think 1989 Subaru that would not let you do that unless throttle was held..

[DragBean]

Perhaps the Acetone could help prevent pre-detonation if it's increasing octane levels and allow you to advance your timing and increase HAI temps?

[ConnClark]

Please don't bump sham methodologies. It gets people to think they might work.

Adding acetone to fuel does nothing good for economy and damages fuel system components.