It was only a week or so ago that I came across the newly-coined word ‘hypermiling’ in an automotive blog. It’s the art/science of driving your unmodified car in such a manner as to get the absolutely best fuel economy possible. Now, we all know the basic rules: avoid jack-rabbit starts, stay at 55 on the highway, and so forth. And probably most of us, especially those who are <ahem> spirited drivers, give the rules fairly short shrift. Hypermilers (www.hypermiling.com), on the other hand, push these rules to the limit.
I happen to enjoy driving. And, being an engineer, I was a bit skeptical of the claims of a recent hypermiler of getting more than 30 mpg on a coast-to-coast trip in a 3.6 liter Ford F150 pickup truck, with an EPA rating of 16/22 city/highway) (tinyurl.com/43h29bo). Now, admittedly, these folks used a bunch of techniques that definitely fall in the category of ‘don’t try this at home’, like shifting into neutral and shutting off the engine on downgrades. But it all got me wondering just how much driving technique really does affect fuel economy.
The test bed for my experiment was my 2.0 liter 2007 stick-shifting SAAB 9-3 turbo convertible. It’s got a few things going for it, such as a turbo and a manual transmission with an overdrive sixth gear. On the other hand, being a convertible, I’m lugging around 3530 pounds, even before adding a driver and passengers. Fortunately (for this experiment, not for me) I make an approximately 350 mile round-trip 80% highway, 20% local drive about once per month. And as the car has an average-reading fuel economy display, I was all set to experiment.
Historically, when I drive my usual style (enthusiastic, but not aggressive), I’ve averaged about 26.7 MPG on the trip. As the EPA says I should be seeing 18 MPG city, 27 MPG highway, that doesn’t seem unreasonable. Pretty good, actually.
For the Experiment, I adopted three fairly straightforward techniques:
The first was to shift at as low an RPM as I could, consistent with not lugging the engine. Obviously this wasn’t possible on highway on-ramps, but ‘Fast and Furious’ near-redlining through the gears would definitely be a no-no.
The second technique would be to never use the brakes. And just as obviously, this can’t be done to perfection either; it’s actually more of a philosophy than a technique: anticipate slowdowns and begin them early, slow well ahead of red lights so maybe they turn green before you get there, and if you can safely maneuver around highway traffic instead of braking, do so. This definitely requires more attention than usual, but that may not be a bad thing in its own right.
The third technique would be to use the cruise control whenever possible. It accelerates and decelerates more smoothly than you do (note that I did not say than you *can* do, but than you actually do), and it certainly holds a steady speed more accurately. Using it to accelerate and decelerate as well as maintain speed on the highway was reasonably easy, once I got used to it, and there were stretches of more than an hour when I didn’t touch the brake or gas pedals at all. Admittedly, this is easier when there’s no traffic.
I’ll also admit to shifting to neutral while rolling down some long hills, but this seems more natural with a stick shift than an automatic.
So what was the bottom line? Actually, I was quite pleasantly surprised. Door-to-door, mixed highway and city driving, with highway driving at the same speed as the traffic (typically 65-70 MPH) I was able to increase my average fuel economy from 26.7 to 31.7 MPG, an almost 19% percent improvement, and 17% better than the EPA highway estimate. And a side-benefit is that if you own a vehicle that can adapt to a range of fuel octane grades (like the SAAB), if you’re not driving for performance, you can burn cheaper fuel as well. Check your owner’s manual.
Am I ready to drive like this all the time? Probably not – after all what’s the point in having a car that’s fun to drive if you don’t drive it in a way that’s fun. But the 80/20 rule applies; on the highway, it’s no big deal to get it up to speed, shift into 6th gear, engage the cruise control, leave it that way for the trip, and save a few bucks. And actually, I discovered that ‘amateur hypermiling’ can be satisfying in its own right. Possibly more satisfying, even, than owning a Prius.
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