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Lorin Thwaits A geek says what?

We'd all like to get better mileage, some just for the pocketbook, and others for the environment as well.  Where I live in Phoenix the ground-level ozone is atrocious, and I'd love to have any other option than burning a gallon and a half of gasoline a day to get to work and back.  So what to do?  Mass-transit doesn't have mass appeal due to how infrequent the service is.  And it's often tough to keep consistent when ridesharing.  So lots of us drive solo to the office.  Well, there are still a few things you can do to maximize the mileage.  In this video a guy talks about proper tire pressure, ditching extra weight, turning off the car at stoplights, and something else most people would never think of -- pouring a little nail polish remover into the gas tank.  Seems like half the people who tested this came up with better mileage, and half with worse, at least according to this wiki.

So after seeing the debate out there, I got curious last weekend and decided to do a quick test, one of those standard before / after tests.  Folks say that adding one ounce to ten gallons of gas gives a modest improvement, 2 ounces usually a little more improvement, 3 ounces and up it starts to peak and then you get less mileage overall the more you add.  So most folks recommend sticking to 2 ounces or less when you do this.   Less acetone sounds good to me because with too much I'll bet it would dry out the plastic and rubber parts in the fuel system.

So last weekend I set up a camcorder in my car to record the mileage readout on the dash.  I've got a Volvo V70, and it has what seems to be a pretty accurate reading of the "instantaneous" mileage you're getting, updated every 2 seconds.  I chose a specific 4 mile run on the freeway to do the testing, and after driving the car a good 10 miles to get it warmed up, put the cruise control on 65 mph, made sure I wasn't drafting anyone, and recorded the mileage reading in that specific stretch of freeway.  The A/C was off, the windows were mostly up, and it was 100 degrees outside.  (10pm in Phoenix.  During the day these days it gets up to a hellish 118 degrees on the freeway.  So these tests are best done at night or in the early morning.)  I made sure all my tests were done with those same conditions, and with the same brand of fuel in the car, for what is hopefully a reliable test.

Well, after playing back the tape from the camcorder and averaging the 127 readings from the first run, I got 37.28 mpg according to the car's computer.  A bit better than my average freeway mileage both because I was going slower than my normal 75 mph pace on the road, and that stretch has a slight downhill grade.

At that point I had about 5 gallons of 91 octane gas in my tank, and I went to the local gas station.  Before pumping anything I added just an ounce of acetone (30 ml), carefully measured with a syringe.  Then I put in another 5 gallons of gasoline from the pump, thinking that it would mix the acetone in better that way.  I drove for 10 miles before my next test, and then went to the same 4 mile stretch of road, the same speed on cruise control, and recorded the mileage.

After averaging the 127 readings from this run, the run right after having added 1 oz of acetone, I had gotten only 34.86 mpg, which is 6.5% WORSE!  That was discouraging.  The Mythbuster guys did an episode on acetone, and had the same kind of results.  But it seems like they didn't do a long-term test.  Some other folks on the 'net had said you may see a little decrease at first, and then an increase after a couple of tanks.  Hmmm, that variation sure makes me think it's the result of cleaning crap out of the fuel system!  I also wonder if the oxygenated fuel we get here in Maricopa County may skew things.  It's 15% ether during the summertime.  We sure don't want that stuff getting in the ground water...  Ether is pretty bad for the nervous system.  Anyway, fuel toxicity is another story for another day.  But relevant to mileage, FWIW the gas is oxygenated year-round out here, half the time with Ethanol, and during these summer months with fairly dangerous ether (MTBE).

So those two tests were last weekend.  And during the week it's been a fairly normal week for driving, errands all around, and lots of preparation for yesterday's Uber 07 event where we had Stefan Schackow and Scott Guthrie out to luxurious Symphony Hall.  This morning I had clocked 300 miles on that acetone-laden 10 gallons of gasoline, and the tank was just about empty.  This morning with only a half gallon left I did the same run, same temperature, same speed, same 127 readings, and got 38.84 mpg!  4.2% better than the first non-acetone run earlier in the week.  I don't know if perhaps the acetone had just cleaned my injectors so they're now working better, or if it's really atomizing the fuel better.  I'll have to do another test like this in a few weeks and see.  Eventually I also want to test with 2 oz of acetone instead of just 1 and see what difference that makes.  Before going nuts with the testing I hope to somehow tie into the knock sensor to make sure there's no extra pinging going on.  Being a turbocharged car that pushes a full bar of pressure (15psi) if it knocks at all it could really ruin the rings fast.

Anyone else out there with a curious bone in their body, fed up with these fuel prices, and willing to experiment with acetone?

Posted on Friday, June 29, 2007 3:44 AM Automotive , Efficiency | Back to top


Comments on this post: Can adding acetone to the tank save you money at the pump?

# re: Can adding acetone to the tank save you money at the pump?
Requesting Gravatar...
You don't think that it was because you had a lighter car on the last test? i.e. Almost no fuel in the tank. Or doesn't that make a difference?

I'm sure you've noticed the acceleration change on smaller cars when you change the tank from empty to full - although you would feel that in your car.
Left by Guy Ellis on Jun 30, 2007 12:08 AM

# Weight -- a very good point
Requesting Gravatar...
Guy -- Good point about weight. Thinking back on it, I actually had 2 more people in the car for the second test. The freeway is pretty danged flat, with just the slightest downhill grade. Less than 0.25% anyway. For those out there familiar with Phoenix, the test was done on I-17 southbound between Bell and Dunlap.

The car coasts amazingly well, so any extra weight on that slight downhill grade may actually cause slightly better mileage rather than worse. All my measurements were done starting with the car completely up to speed, so that avoids pretty much all the negative impacts of having the car more weighted down.

In the two parts of the first test the weight of the added gasoline should be negligible. After all, curb weight for this car is 3368 lbs, so after adding 30 pounds worth of gasoline (the 5 gallons worth) the overall weght increased by a little less than 1%.

But for that second test having 2 more people in the car, and adjusting for the 60 lbs less fuel (the 10 gallons being depleted), overall there was about 160 lbs more weight compared with the first 2 tests. That's actually 4.7% more weight on the second run. Now I wish I had been more meticulous in adding just 60 pounds more to the car for that second test instead of 160. That does skew it a bit.

I'm still thinking at less than 0.25% grade the factor of weight is almost moot, and there would have been better mileage even with the exact same weight. I'm still working under the assumption that the better mileage is primarily from the acetone cleaning out the injectors, giving a better spray pattern and thus better atomization of fuel.
Left by Lorin Thwaits on Jun 30, 2007 1:25 AM

# re: Can adding acetone to the tank save you money at the pump?
Requesting Gravatar...
That last sentence in my last comment was meant to read that you probably would NOT feel it in your car but I'm pleased however that you discovered an inconsistency with two lightweights in your car judging by their combined weight.
Left by Guy Ellis on Jul 08, 2007 1:50 PM

# re: Can adding acetone to the tank save you money at the pump?
Requesting Gravatar...
dude, seriously... it's a load of crap.

http://www.msnbc.msn.com/id/18909941/
Left by Ryan on Apr 13, 2008 8:12 AM

# re: Can adding acetone to the tank save you money at the pump?
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I have read elsewhere that ethanol completely negates the effect of adding acetone. The best explanation I have heard is that the acetone improves vaporization. The improvement to vaporization is purportedly achieved by reducing the surface tension of the gasoline by adding the acetone. Ethanol has been consistently shown to reduce surface tension, so the idea here is that it will completely negate the effect of the acetone. If you are really ambitious at figuring things out, you might try using the acetone and filling your tank exclusively at stations that do not include ethanol in the fuel. I know that some states actually have laws requiring ethanol in all gasoline so perhaps this isn't possible for you. The other thing here is that one tank of gas is not enough to establish a reliable measure of fuel economy. There is additional evidence that suggests that the efficacy of fuel additives like acetone varies considerably based upon the compression ratio of a particular vehicle. This is also consistent with the hypothesis regarding vaporization.

Left by Adam on Jun 06, 2008 9:49 AM

# re: Can adding acetone to the tank save you money at the pump?
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# re: Can adding acetone to the tank save you money at the pump?
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# re: Can adding acetone to the tank save you money at the pump?
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