Fifty dollar fill-ups are what you might call an incentive. That's how some self-described "hypermilers" look at it, anyhow. These folks will do just about anything to eke another mile out of a $3 gallon of gasoline, including emulating the race car driver's trick of "drafting" by riding up close behind a tractor trailer to take advantage of the truck's air vortex, which pulls the following vehicle along in its wake.

Of course, if that big rig slows down suddenly, the repercussions of following too closely could be ugly. Still, some of the practices espoused by the fuel-conscious hypermilers (see www.cleanmpg.com) are perfectly sensible - and perfectly doable.

For example, maintaining momentum.

If you see a red light up ahead, let the car slow gradually instead of rushing up to the light and having to come to a complete stop. If you time it right, you'll still be moving when the light turns green again. And it takes less energy (and burns less fuel) to resume speed from a "rolling start" than it does to get it going from a dead stop. On roads you travel every day, it's often possible to learn the rhythm of the lights - and pace yourself so that you never have to actually stop completely. In addition to saving some gas, you'll also reduce the wear and tear on your brakes and tires - and the money you save that way could mean an extra "free" tank or three every year.

If you do have to come to a complete stop, try to anticipate the green by watching the opposing signal. Most drivers don't pay attention - and it takes them a second or so to notice the light's changed. Then they punch it to make up for the second or so they lost - wasting a lot of gas along the way. But if you're ready to get going as soon as the light goes green, it's usually possible to achieve the same result without having to floor the gas pedal. You can accelerate up to speed more gradually - yet not impede the flow of traffic. (Saving gas is great; aggravating your fellow motorists in the process isn't.)

According to the EPA and other sources, simply driving smoothly can improve overall fuel efficiency by as much as 10 percent.

On the highway, try to maintain a consistent speed. You can do this by not following other cars too closely, which leaves you sufficient cushion to gradually slow down (if need be) and then accelerate (gradually) as necessary to keep with the flow of traffic. If you have cruise control, use it.

And much as we find it tedious, it's also fuel-smart to avoid driving faster than about 55-60 mph. At speeds over 70 mph, fuel economy begins to suffer - badly. We may get where we're going more quickly (and have more fun getting there) but there's a price to be paid for the indulgence - and you'llpay it at the pump.

Keeping your tires properly inflated is another small thing that can pay big dividend - both in terms of fuel economy and tire wear.

The hypermilers have achieved some especially spectacular results using these fuel-miser techniques with hybrid cars - getting as much as 75 mpg, in the case of Texas resident (and Honda Insight driver) Chuck Thomas. One Toyota Prius owner claimed 112.2 mpg on the web site, www.greenhybrid.com - which is more than twice the generally reported "real world" mileage most Prius drivers are seeing in combined city/highway driving.

The pace may be slower - but the gas bills are lower.