Raw data

For posterity, I thought I'd post the results from the beginning of my effort. You'll see the dates, miles and gallons for each fill up. Also, you'll see the cumulative days of the experiment and the standard deviation in mileage based on the results of each fill up. Note that no pre-experiment data exists, so you'll just have to take my word that the average mileage at that time was 14.9 m.p.g. based on the "average mileage" readout of the display unit in the car. I'd like to include graphs, but I haven't yet been able to figure out how publish them in a readable fashion. Sigh...

Date	Miles	Gallons to fill	Mileage	5-tank mov. Avg.
9/5/05	377.2	18.714	20.16
9/9/05	346.7	19.541	17.74
9/16/05	381.5	18.948	20.13
9/24/05	404.3	20.126	20.09
10/1/05	401.3	18.293	21.94	20.01
10/8/05	414.1	19.821	20.89	20.16
10/14/05	429.6	18.545	23.17	21.24
10/28/05	401.0	20.399	19.66	21.15
11/6/05	446.1	20.703	21.55	21.44
11/16/05	443.8	19.190	23.13	21.68
11/23/05	403.2	19.821	20.34	21.57
12/3/05	425.2	19.299	22.03	21.34
12/14/05	434.1	19.044	22.79	21.97
12/21/05	414.7	19.484	21.28	21.92
12/29/05	442.2	17.604	25.12	22.31
1/6/06	404.4	19.777	20.45	22.34
1/14/06	415.8	18.904	22.00	22.33
1/19/06	438.9	18.739	23.42	22.45
1/27/06	454.7	20.066	22.66	22.73
2/5/06	415.0	19.402	21.39	21.98
2/14/06	432.3	20.252	21.35	22.16
2/21/06	437.8	20.282	21.59	22.08
3/2/06	454.2	20.261	22.42	21.88
3/9/06	435.2	19.351	22.49	21.85
3/22/06	444.0	20.321	21.85	21.94
3/30/06	456.7	21.321	21.42	21.95
4/6/06	456.4	21.361	21.37	21.91
4/17/06	444.7	19.291	23.05	22.04
4/25/06	475.5	20.099	23.66	22.27
5/2/06	416.0	16.217	25.65	23.03
5/11/06	416.8	19.624	21.24	22.99
5/20/06	482.3	20.322	23.73	23.47
Totals:	13645.7	625.1	21.83
Standard deviation:		1.60	m.p.g.
Days of experiment:		257

Dilemma

I'm having trouble now deciding if I'm in the midst of an experiment or just trying to save all the gas possible. If it's the former there are several things I'd like to try, but I'm loathe to see the "average mileage" display creep down as I test hypotheses.

What hypotheses? The least likely to reduce my mileage has to do with fuel in the tank. I've always heard gas mileage is better during the first half of a full tank. The fuel gauges of all the vehicles I've owned act this way, but I suspect that that behavior is an artifact of the gauging mechanism. After all, half a tank weighs less than a full tank, and though the air doesn't know how much the car weighs so drag won't change, it does take more fuel to accelerate a heavier car. Further, increased weight adds to the tire loading, thus increasing road loads. I suppose it's possible that a larger hydraulic head in a full tank could somehow improve pumping efficiency but it seems far-fetched.

I'm a pilot, and I know from that avocation that fuel weighs about 6 pounds/gallon, so a full tank (21.5 gallons) in my car weighs about 129 pounds, the weight of an extra adolescent or perhaps female passenger. So it stands to reason that mileage would improve as fuel is used.

Finding out would take quite a while, filling and emptying to half a tank is not as exact as topping off to measure fuel usage. I'd fill to full, drive until I get as close as possible to, say, 5/8 full and refuel. I'd do this maybe 15 times, and calculate the mileage at each fill up. Then I'd drive down to 1/8 tank, add fuel to bring it to 1/2 full, drive down to 1/8, repeat, etc. Again, I'd do it maybe 15 times and compare. It wouldn't be exact because of the difficulty of filling and reading to exact level using the gauge but after sufficient trials, a conclusion should be possible.

Or perhaps the best way to measure this, since full tank is the easiest level to which to accurately fill, would be to run a series of trials, always filling the tank but alternating between using about 1/2 of a tank and close to a full tank. This way the accuracy of the miles per gallon achieved would be maximized, but the difference in the results would be minimized. Well, if I do the experiment I'll put a lot more thought into its design.

What else? I've achieved what I regard as a drastic reduction in fuel consumption by taking many different steps, as detailed elsewhere in this blog. Which of the measures are most effective and which are minor? Is it the slow acceleration that contributes the most, or perhaps the reduced freeway speed? The way to find out is to eliminate each measure I've taken, one at a time, and measure the result. Unfortunately, at least one or two of the experiments would likely lead to my having to watch the "average mileage" indicator show significantly deteriorating results, and I just hate to give back my hard won tenths of a mile per gallon.

Maybe I AM eccentric.

Proselytizing

In my previous post I expressed my skepticism that the U.S. would find the will to take even a significant portion of the measures I have undertaken to save gasoline. Part of my skepticism stems from a general feeling about "the way things go" and part from my experiences with friends, family and people at my company.

I've made no secret of my program. To some of the people I mentioned above saving something like $1,500.00 per year doesn't mean much. To others, it's a large amount, enough to make a difference in their lifestyle. But to a person, they all shake their heads and tell me they couldn't do it and explain to whomever is around that "Rob (I'm Rob) is eccentric."

A man who works at my company drives a big Ford dually pickup with a large diesel engine. He's put a chip in it to maximize performance and that sucka will most definitely hurry up. He commutes from Riverside, CA to Long Beach each day, a round trip I'd estimate at about 100 miles. He makes decent money but he just bought a house and at times is strapped.

I asked him today what it costs him to fill up and he told me $120.00. He's known from the outset of my experiment, he and I used to race each other. He's always just shaken his head about what I'm doing now, so I thought I'd present it to him and his buddy in a different way today. I said "you know Tim, driving this way I get the equivalent of every third tank of gas free." He acknowledged that that was an interesting way of looking at it, but it didn't change his behavior.

There was a song a while back called "I Can't Drive 55" by Sammy Hagar. I know that the vast majority of people feel that way and even with government action I don't see how people will adopt these habits. And as I mentioned in a previous post, I tend toward Libertarianism. So all in all, I'm probably tilting at windmills. But I'll continue to tilt at these and to look for others at which to tilt.

I think next I'll spend some time thinking about "unintended consequences."

Best case scenario

In my last post, I conservatively estimated that the U.S. would be able to immediately reduce its need for imported oil by about 5% by changing non-commercial driving technique in a mostly benign way. What about an optimistic yet not, in my opinion, pie in the sky estimate?

Well, I'm now at 22.7 m.p.g. in my 2000 Jeep Grand Cherokee Limited. The E.P.A. says I should get 15 m.p.h. city and 20 m.p.h. highway. I estimated in an earlier post that 36 out of every 60 miles I should be getting "highway mileage" and 24 out of every 60 miles I should be getting "city mileage." So a weighted average E.P.A. estimate for my driving regime would be (36/60)*20+(24/60)*15=18 m.p.g. But I've demonstrated that it's possible, with this driving regime, to get 22.7 m.p.g. at least.

Now, the vast majority of people to whom I've talked, about whom I've read, etc. complain that they don't achieve the E.P.A. estimates. Let's say the average is 90% of the E.P.A. estimate. I'm getting 126.1% of the E.P.A. estimate for my car. Suppose everyone went from 90% to 126.1% of the E.P.A. estimate. That would result in a 40.1% increase in gas mileage nationwide or a decrease to (1/1.401) times 100% = 71.4% of the fuel used before the change. That is, personal transportation fuel use would be reduced by 28.6%.

Using the figures in my previous post, that would result in a reduction of .286 times 6.4 Mbbl/day or 1.83 Mbbl/day. That's about 13.9% of our daily oil imports. Now we're getting someplace. All this without a single person driving a single mile less than they are currently driving or buying a more fuel efficient vehicle. And remember, this completely leaves out commercial use of transportation fuels.

Can it happen? Yes, of course. Look at the rationing during World War II. Will it happen? Probably not, but something much more onerous surely will.

So what?

OK, so I started this driving experiment in August 2005 and I've saved 15 tanks of fuel or so. What does that mean? It's a difficult subject. It's not likely to postpone the onset of the effects of so-called "peak oil," even if I could get everyone in the country to do it. A case can be made that, if everyone in the U.S. started driving the way I've driven during this experiment, it would have a very measurable effect on the need for imported oil. Alone, it wouldn't stop it but it would be significant.

But what would it accomplish? Well, reduction in the U.S. demand for imported oil would presumably lower the price or at least influence prices in a downward direction, thereby encouraging consumption in China, India, etc. Clearly, the path these "developing nations" are on is leading them to find plenty of ways to use oil, and a lower price would accelerate that process. Even so, I believe that huge advantages would still be gained for the United States.

Let's look at some numbers. It's not easy (for a layperson such as myself anyway) to find definitive numbers for some of this, but I've given it my best shot. Should anyone have better information, I would welcome it.

Of the approximately 20.5 Megabarrels/day (Mbbl/day) of oil used in the U.S., about 13.7 Mbbl/day goes to transportation. As best I can determine, something like half of that, or 6.4 Mbbl/day goes to "non-commercial" transportation. This is where I make my impact. Suppose all the drivers in the U.S. took the "realistic" approach I mentioned in my first posting in this blog and that my estimates are correct. I had felt that a 15% gain in average fuel economy was reasonably achievable, but let's be more conservative. I believe that 10%, or .64 Mbbl/day could easily be saved. That amounts to about 5% of our oil imports.

What??!! Reducing speed from 70 m.p.h. to 55 m.p.h., avoiding drive-through windows and other unnecessary idling, judicious use of the gas pedal, etc. is only good for a 5% reduction in import demand? And EVERYONE would have to do it?? Well, it is one of many relatively painless steps that can be taken.

Suppose we really wanted to end our dependence on oil imports. If, instead of increasing our oil consumption annually, we reduced it by 5%, we would eliminate our dependence in 18 years. This assumes that U.S. petroleum production remains constant.

Of course, the reduction attained by conservative driving techniques represents 5% of imports, not 5% of consumption. So that, along with some other measure, would be the steps to be taken on the first of the 18 years. They only get harder after that.

I've carefully avoided controversial political aspects of oil use. In particular, I've brought up neither "peak oil" nor "greenhouse emissions" in this blog prior to this post. I started my experiment simply as a way to see how much gas (and money) I could save and at what cost in terms of frustration. The answer is that I can save about 500 gallons or over $1,500.00 per year. And though I've experienced very little frustration, I suspect I have frustrated some of those who have ridden with me and I'm certain that I've frustrated some of my fellow drivers.

Still, I believe that this is important. It has genuinely changed my outlook on my energy budget. I have become much more aware of my personal "energy leaks" and the leaks of my business and those around me. Much more will be required, but I won't dismiss the value of this small experiment in efficiency.