photo credit: joguldi

No, this isn’t another story about Char and I taking a joy ride in an unattended golf cart. We’re grown up now.

There was a recent article in the Wall Street Journal about how a few Texans have taken to driving electric golf carts because of high gas prices. These cars seem limited to city driving since their maximum speed is only 25 mph and they have a range of just 30 miles. Still, they’re only paying 2 cents per mile compared to 20 cents per mile for a car that gets 20 mpg. For one person in the article, that equates to saving $100/month. With savings like that, the cars, which cost only $7,000-$18,000 nearly pay for themselves.

In DWT’s inaugural post, Graham talks about his introduction to Texan culture, especially on the roadways, and how it spawned DWT. Coming from California, he was amazed at the disparity with California’s “oppressive traffic enforcement”. Well, I’m a born and raised Texan, so it comes as no surprise to me that people were defiant towards a decrease in the speed limit. Heck, people ignore the speed limit when its 65/70 (in one week all the men in my family got speeding tickets; coincidentally, none of them were our fault). All too often I’ve been driving down the highway going the “speed limit” only to be passed like I’m standing still. And not by a Ferrari but by a soccer mom in an Escalade.

But what happens when you pit a Texan’s love for driving whatever speed we want, against our pocketbook?

Recently, Senator John Warner suggested studying the feasibility of a return to a federally mandated speed limit to allow for a decrease in nationwide fuel consumption. I thought of the repercussions here in Texas. Let’s assume that we returned to the a federally mandated speed limit of 55 mph, as it was in 1974, would Texans respond given the high gas prices?

The Houston Chronicle conducted a recent survey (not entirely robust, but it works) by driving 60 mph on the major freeways in Houston to determine the average rate of travel of fellow drivers. The ratio on one day of being passed to passing others was 478:0.

Texans won’t slow down, even in the current climate of exorbitant gas prices. So it would seem, Lyle Lovett could easily have written “Don’t Touch My Speed Limit” instead of “Don’t Touch My Hat.”

Now let’s get to some sciencing. Most fuel efficiency sites I read online cite this number, and there is even a graph on a Department of Energy website () which shows that indeed fuel efficiency is maximum at 55 mph. I found this exact same graph in their annual Fuel Economy report since 2003. Is it me, or should this graph deviate slightly from year-to-year?

The scientist in me wants to know: when the study was commissioned, how many vehicles were studied, and the types of vehicles. None of which were given. As you would imagine, fuel efficiency, and the relationship with efficiency in speed is highly dependent upon the car. You have drag, weight and engine issues to consider.

I can’t help but think that automobile engineers have the specs dialed in for each car to achieve the highest efficiency at common highway speeds (i.e. ~70 mph). This is indicated by any ECU changes that can easily be made to most cars to increase horsepower and torque, but only at the detriment of gas mileage. My Volvo s60R has a slightly higher tuned engine than the average car and I achieve the same MPGs at 85 that I do at 70, 65, and 60. This makes me think that instituting a (lower) federal speed limit would only serve to increase the amount of money local governments get due to speeding tickets.

I think an emerging trend I would like to see would be to have MPG vs. Speed curve for every car, much like most performance automobiles have horsepower and torque curves. That way you let the individual decide which is the optimum speed to drive for their car. Everybody wants better gas mileage, so put that decision in their hands.