Hypermiling is the latest vogue approach to maximizing fuel efficiency with extreme driving techniques and vehicle modifications. The father of hypermiling is arguably Wayne Gerdes of Wisconsin, who boasts of such achievements as getting 59 miles pergallon in a non-hybrid car. There are now websites dedicated to hypermiling, complete with message boards on which drivers discuss the latest theories, techniques and accomplishments.
The hypermiling techniques employed by guys like Gerdes include such things as driving with windows up (to minimize wind drag) and with the air conditioner off (to minimize fuel consumption); tailgating trucks; turning the engine off at any time the car stops for more than a few seconds; and even turning the engine off while driving on down grades. Gerdes takes if much further by, for example, trying to coast to stops without using his brakes at all.
Still other approaches include vehicle modifications. Some hypermilers like to install wheel covers to prevent wind from entering the wheel areas and creating drag. Some go so far as to block off the vehicles grill, again to minimize wind drag. So clearly the techniques run the gamut from odd to outright dangerous.
To hear the hypermiling believers talk, it is all well worth it as the techniques produce markedly increased fuel efficiency. But do they really? As someone who has experimented with many of the suggestions, I find the results mixed at best. Admittedly, I’ve never taken things to quite the Gerdes extreme, but I have applied most of the techniques over the course of multiple tanks of fuel. Suffice it to say, my results vary from those boasted by hypermile advocates. In city driving, I accomplished only about a 2 mpg increase. Highway driving does see a better improvement, perhaps 5 -6 mpg. Here are my thoughts on some of the more common techniques:
Cutting the engine off at stops
I’m generally not a believer in this approach, unless you know you are catching the entire red light cycle of a known long light. Gerdes says that he kills the engine if the light or stop will be for more than 7 seconds. I don’t know why he decided to draw the line there, but I can’t imagine it’s worth it. I say this because if you truly restart the engine that frequently, you are probably going to be buying a new starter every 10,000 miles. That violates one of our fundamental rules of frugal living, which is the need to think it through and look at the bigger picture.
My practice is to turn the engine off if I know I am going to sit for at least a full minute. That is generally only the case at a handful of traffic lights at major intersections.
Cutting the engine off while driving
The basic theory here is that by shifting to neutral and cutting the engine off, you can steal miles without burning gas at all. While an appealing thought, it is generally not a good idea at all. Why? Because when you kill the engine, you will have only a few pumps of power braking left. After that, you will have to press the brake with much greater force in order to stop or slow. You also lose your power steering, which can be a frightening thing if you are on a curvy road.
Admittedly, I do occasionally apply this technique when coasting down grades with which I am very familiar and comfortable. But it needs to be a fairly long one to make it worthwhile. (See starter discussion above). So if you have mile or so downhill stretches on your regular commute you might want to experiment with this technique. Note too that this combines well when you have a long downgrade that ends with a traffic signal. That way you can double up on the benefit by picking up a free mile or so and avoiding any consumption of gas at the light, all with a single engine stop and start.
For shorter hills, the better approach, in my opinion, is to simply shift to neutral while leaving the engine on. This “free wheeling” approach gives you most of the same benefit without the wear and tear on the starter and without losing power brakes and steering.
Windows up and a/c off
Thumb down to this idea, at least in the southeastern U.S. where I live. Again, this site is about practical frugal living. Driving around in a self-imposed sauna and arriving at work wet is not a practical approach to living.
I hate to admit it, but this one is a tough call. From a safety standpoint, it is definitely not a good idea. Not only does tailgating significantly increase the risk of accidents, it really pisses off other drivers, thus also increasing the risk of road rage.
And yet drafting off of a larger vehicle also works. In fact, of all the techniques discussed, this is the one that has produced substantially elevated fuel efficiency for me during highway driving. Nothing will boot miles per gallon greater than finding a nice large tractor trailer and following closely behind it for 30 or 40 mile. And you don’t have to follow that close to see the benefit. A one second following distance produces results. Closer is better, but more dangerous. In fairness, I should note that truckers hate this practice, and we can understand why. But if you keep the one second following distance it’s not that bad. I also try to spread it around, following different truck every 8 – 12 miles or so.
So what is the bottom line on hypermiling? It works, to some extent. Most of the techniques, in my opinion, are not worth the trouble, risk and larger picture expense. They also pale in effectiveness compared to the simple approach of regularly maintaining adequate tire pressure with a simple tire gauge. Incorporating a few of the suggested methods, however, does have a place in the art of practical frugal living.