Honda Insight(Photo: Honda)

The Honda Insight is a popular vehicle amongst hypermilers, individuals who seek to eke the most out of every litre of fuel.

Don't be so sure that the seemingly erratic or trance-like behaviour of that driver in front of you is caused by senile dementia or the illegal ingestion of mind-altering substances. There may be method in their madness. The driver in question might even be highly skilled and intensely focused on what they're doing. He or she might, in fact, be hypermiling.

You're forgiven if that explanation leaves you none the wiser. The word has only existed about five years. It was coined in 2004 by Wayne Gerdes on his web site CleanMPG.com. The word has gained a lot of currency, though, since the Oxford American Dictionary choose hypermiling as its 2008 Word of the Year.

Hypermiling is an informal movement of environmental and conservation zealots dedicated to maximizing the fuel mileage (or, in metric terms, minimizing the fuel consumption) of their rides. Most of them drive cars that are outright gas misers to begin with. Many also modify their cars to make them more scrooge-like still. And all of them practice driving techniques designed to wring every last drop from each litre of fuel.

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Slow and steady is just the beginning

A big-rig 18-wheeler

Drafting is a common hypermiling practice, but be careful - it is dangerous.

Simply driving slowly - at or below the speed limit - is merely the tip of the hypermiling iceberg. Other techniques can include pulse-and-glide (alternating between brief bursts of acceleration and longer spells of coasting), a slow-up, fast-down approach to driving through hilly terrain, or keeping up speed through tight curves so as to mimimize the energy needed to regain cruising speed on the next straightaway.

Conservation of momentum is the goal. Nothing wrong with that, when it means scanning the road far ahead, so you can get out of the gas early and approach an unavoidable halt - for example a stop sign, or a traffic light just turned red 500 metres up the road - on a closed throttle.

Still, the techniques can tick off other, less-enlightened drivers who are following the hypermiler. And when they go to extremes, hypermilers may be tempted not to stop at all, even when the law requires it. Another hypermiling practice - getting an aerodynamic "tow" from eighteen-wheelers by tucking in close behind them - can also bring hypermilers into conflict with safe driving practice.

Hurry up and save fuel

Tire pressure

Maintain proper tire pressure, but don't over-inflate.

At various times and in various countries, economy driving was or is still is a competitive sport. And no, the winners are not those who simply have the patience to drive the slowest. Competitors have to maintain a minimum average speed, and said speed is usually quite challenging in relation to the back-roads terrain being covered. Remember the bit about keeping up speed through curves? Small wonder that some of the most successful economy-run competitors are pro race drivers.

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Toyota Prius(Photo: Toyota)

An efficient car such as the Toyota Prius is a good starting point, but hypermilers will often modify their vehicles to be even more efficient

Today, dedicated hypermilers gather on Web sites like CleanMPG, ecomodder.com, and autobloggreen.com to share their results. Often they express them as a percentage improvement over the EPA or Natural Resources Canada (NRCan) ratings for their vehicles. That way, even drivers of relatively thirsty vehicles can feel a sense of achievement.

More typical vehicles of choice naturally include the Toyota Prius or Honda Insight. Those less pecunious are buying up surviving examples of the Honda CR-X, or those GM/Suzuki three-cylinder subcompacts (Geo Metro, Suzuki Swift etc) of the '90s.

Then they go to work on making their gas misers even miserly-er. Hypermilers obsess over tire rolling resistance, and the weight of their wheels and tires. They may remove air-conditioning systems (if installed), relying on beaded seat covers to handle the heat. Alternate gear ratios in the transmission help lower cruising rpm, and lowered suspensions help reduce frontal area. Other aerodynamic tweaks can include installing spoilers and flush wheel covers, or removing door mirrors.