gwax's rumblings

As of the most recent refill of my truck’s gas tank, I am con­fi­dent that I have enough data to draw some con­clu­sions about the effect on fuel econ­omy of using ace­tone as a fuel additive.

To recap, for any­one that might have for­got­ten or missed out, a num­ber of months ago, I came across the sug­ges­tion on the inter­net that fuel econ­omy could be improved by using a small quan­tity of ace­tone as a fuel addi­tive. Since I wasn’t ter­ri­bly con­cerned about the risk of break­ing my truck and des­per­ately wanted a way to save some money on gaso­line, I fig­ured I might as well give it a shot. I started out by buy­ing a gal­lon of pure ace­tone and adding a lit­tle bit by fun­nel every time I filled my gas tank (before the gas to encour­age mix­ing). Initially I saw what might have been an improve­ment in fuel effi­ciency but I was rely­ing on my mem­ory and quickly saw my infor­ma­tion as purely anec­do­tal. Understanding how use­less anec­do­tal infor­ma­tion is, I decided to approach the mat­ter in a sci­en­tific and con­trolled man­ner. Now, 22 tanks of gas and nearly four months later I am ready to draw con­clu­sions from my data.

I have found a near lin­ear increase in fuel effi­ciency up to a peak increase of about 10% at a con­cen­tra­tion of ace­tone of 0.2%. Further increases beyond 0.2% result in a very steep fall-off in fuel effi­ciency such that a con­cen­tra­tion of 0.25% is less fuel effi­cient than no ace­tone at all. For those that don’t want to think about con­cen­tra­tions, 0.2% ace­tone is almost exactly equal to 1/3 cup ace­tone for every 10 gal­lons of fuel.

Just to be polic­i­tal, or some­thing like that, for a moment, if I can fina­gle a 10% increase in my fuel econ­omy out of ¢10 worth of ace­tone, I am doing a huge ser­vice to my bank account and the envi­ron­ment (ace­tone doesn’t pol­lute any more than gaso­line). Now let’s just take a moment to think about how much of an impact there would be on the envi­ron­ment if every sin­gle car in America improved its fuel effi­ciency by 10%; acknowl­edg­ing that, why isn’t there a gov­ern­ment man­date on gaso­line requir­ing it to con­tain 0.2% ace­tone (or there­abouts)? My guess would be because your mon­e­tary sav­ings would come straight out of the oil com­pa­nies pock­ets, but that’s beside the point. I think every­one should start adding ace­tone to their fuel tanks, sav­ing them­selves some money, help­ing the envi­ron­ment and cut­ting back on our oil con­sump­tion. Hmm, maybe I’ll write my senator.

I should like to add the caveat that these results are true for my truck and other vehi­cles may have slightly dif­fer­ent ace­tone con­cen­tra­tion sen­si­tiv­i­ties. If you decide to fol­low my lead and add ace­tone to your vehi­cles fuel tank, you should per­form some exper­i­ments on your own to deter­mine your vehi­cles effi­ciency peak con­cen­tra­tion. You should use pure ace­tone (sol­vent from a hard­ware store), not the scented stuff you can buy at CVS. Also, if you do some­thing stu­pid and blow up your car or some­thing, it’ll be your fault alone.

It’s been a while since I’ve men­tioned my exper­i­ments adding ace­tone to my trucks fuel tank, so just to pre­vent you think­ing I’d given up on the mat­ter, here’s an update. I’ve improved the algo­rithms I’m using in my Excel spread­sheet because I was bored, so now I com­pen­sate for remain­ing ace­tone as a result of refill­ing before the tank it empty, vol­ume of ace­tone added and I get rather more infor­ma­tive analy­ses. Additionally, I’ve added a more data points, putting me at 17 tanks of fuel on the chart. Currently, data sug­gests a near lin­ear econ­omy increase for my truck of about 7% at 0.15% ace­tone con­cen­tra­tion (1MPG at 1/3 cup ace­tone). This lin­ear increase isn’t show­ing any signs of lev­el­ing off, so I’m going to start push­ing the con­cen­tra­tion up in the next few tanks. I’ll give you a bet­ter write up with more man­age­able units when I’m sat­is­fied that I’ve found the ace­tone con­cen­tra­tion of max­i­mal econ­omy for my truck. I expect that I’ll prob­a­bly repeat this exper­i­ment with my next vehi­cle, and every vehi­cle there­after for that mat­ter (as long as they still run on petrol).

I’ve been dump­ing ace­tone into my truck’s gas tank for a while now and I’m happy to report that it appears to be harm­less to the truck: no unex­pected explo­sions, no stalling, no loss of power, noth­ing neg­a­tive. I can defin­i­tively say that the ace­tone has not decreased my fuel effi­ciency, but I can not yet say if it has increased my effi­ciency at all. I’m going to run a few more tanks with ace­tone after I get back to Concord and my dri­ving habits sta­bi­lize (drive to Cambridge, drive back, repeat a bunch). After I get a solid base­line of Concord to Cambridge runs with ace­tone, I’ll do a few tanks with­out ace­tone and see if I can notice a change. In the name of sci­ence I will make a point of get­ting gas at the same gas sta­tion as much as absolutely possible.

I started my test­ing with 1/4 cup ace­tone per 15 gal­lon tank (~1.3oz/10gal), using ace­tone from a 1 gal­lon con­tainer of pure ace­tone that I bought at Wal-Mart for the pur­poses of this exper­i­ment. Using the same ace­tone, I stepped up to 1/3 cup ace­tone per 15 gal­lon tank (~1.8oz/10gal) and con­tin­ued to have no prob­lems. I’m plan­ning to step up to 1/2 cup per 15 gal­lon tank (~2.7oz/10gal) before I start doing my real data gath­er­ing. I may go up to 2/3 cup per 15 gal­lon tank (~3.6oz/10gal) after I get some solid evi­dence to sup­port the effec­tive­ness of ace­tone as a fuel additive.

On Friday, I came to dis­cover that one of my truck’s spark­plugs was dis­con­nected and, likely, had been for the three months that I’ve owned the thing. I recon­nected the spark­plug and it’s been run­ning smoother and with­out the back­fir­ing that I’d grown accus­tomed to. Needless to say, adding another cylin­der is going to change the fuel con­sump­tion char­ac­ter­is­tics of my truck so now I’ve got two inde­pen­dant vari­ables con­tribut­ing to my mileage, which will change the way my sci­ence works. I will fig­ure out a way to account for this and get back to you even­tu­ally when I fig­ure out what, if any­thing, the ace­tone does.

What sur­prises me most is that I’d been dri­ving the truck for about 3 months and the dis­con­nected spark­plug had gone com­pletely unno­ticed by me.