A few weeks ago, I headed to my family's bay house in Kemah for the weekend and needed to stop for gas before making the trip. After leaving over $80 with the station, I thought I would drive to Kemah at the posted speed limit and see how much it improved my gas mileage. I was stunned. I drive a full-size sedan that averages about 20mpg. On the trip to Kemah, I got 32mpg.
On the trip down I was reminded of a recent story in the Chronicle where two reporters had driven all major freeways around Houston at the posted speed limits. Predictably, they were passed thousands of time. Click here to read the Chronicle article.
I had the same experience, as many SUVs and large trucks roared past me at well over 80mph. I wondered if they had any idea what their gas mileage was that those speeds.
After our trip, my wife, Melissa and I decided that we would consciously begin driving in a manner that would improve our gas mileage. At the same time, we looked for opportunities to consolidate trips. Since we have started, our weekly expense has actually gone down. We have cut our gasoline usage by about 20%.
Our experience is confirmed by a number of websites and organizations promoting greater driving efficiency. A good summary can be found at the Department of Energy's site: click here to go to the summary
. There are a number of websites that provide suggestions to improve gas mileage efficiency, but all clearly emphasize that the most important factor in your car's gas mileage is the speed at which you drive
. The basic science behind this is that wind drag on your car increases exponentially with an increase in vehicle speed. So, if you double your speed, the drag is cubed, or 8X greater. This was the theory behind the 55mph speed limit back in the 1970s. To some extent, the inefficiency caused by wind drag is overcome by your car shifting to higher gears. The optimum speed for the best gas mileage is different for each car. But generally, the sweet spot will be somewhere in the 55-65 mph range.
There is a very steep penalty for exceeding this range. The Department of Energy estimates that driving 75mph instead of 55mph, will decrease your gas mileage by about 20%. That is the equivalent of increasing the price of gas by about 80¢ per gallon. In other words, if you would like to lower your gas price from $4.00 per gallon to $3.20 per gallon, slow down to 55-60 mph.
There is another benefit from driving slower. It is safer. Amazingly, we still lose about 40,000 lives each year in traffic accidents in this country, more than 10X all the Iraq War causalities. There are about 500 traffic related deaths annually in Harris County alone. The Houston Galveston Area Council (HGAC) has estimated that about a third of the accidents in our area are caused by excessive speed.
There are also environmental benefits to burning less gasoline. Each gallon of gasoline produces 19.5 pounds of CO2 along with smog producing nitrous oxides and volatile organic compounds.1
If we cut the number of gallons burned each year by 10-20%, it would make a marked difference in our air quality.
But increasingly, I am beginning to feel that conserving gasoline is a patriotic act. Our economy today is in a wreck largely because of our addiction-like reliance on foreign oil. We are paying billions of dollars to other countries for oil that we are literally burning up in smoke. In the meantime, they are recycling those dollars, buying up American real estate and companies. We are being taken over by other countries not by military might, but by our own inability to curb even slightly, our ravenous appetite for gasoline.
The ironic thing is that our reduction in gasoline usage has had virtually no impact on our lives. I do not miss any trips that we have not made. And by driving the speed limit and listening to music or books on tape while I am driving, I arrive more relaxed and rested than when I was pretending to be a race car driver.
Every day, Americans use a little over 9.3 million barrels of gasoline. We have actually begun to reduce our usage already. For the week of June 20, we cut about 200,000 barrels a day from the same week last year. But this is a measly 2%. Just by slowing down and driving more carefully, we could easily save five times that amount.
Today, we are importing about twice the crude oil we were in 1990. Should any of us be surprised that the price is rising? There are many places to lay the blame for our current crisis and many different proposed solutions. Figuring out who should be blamed will never be settled and would accomplish nothing. And, unfortunately, you and I have little influence over what the federal government will (nor more likely will not) do on an energy policy. But there is one thing you and I can do, for ourselves and our country. We can slow down and use a little less gasoline. It hardly seems like much of a sacrifice and is an appropriate way to celebrate our independence.
It may seem impossible that a gallon of gas which weighs about 6 pounds can produce nearly 20 pounds of carbon dioxide, but it is true. For an explanation click here