The most interesting thing I confirmed is that the posted speed limit on the freeway isn't always the speed limit. If all of the cars around me on I-15 are going 80 in a 65 mph zone, and I drive 65, and it makes the other drivers pull around me, I could get a ticket.

SALT LAKE CITY — Cars tend to get better gas mileage going between 55 and 60 mph than at faster speeds. So when an energy crisis in 1973 prompted a conservation mindset, the federal government came up with the National Maximum Speed Law that capped speed limits around the country at 55 mph.

The forced conservation initiative created a lot of energy — under the collar of America's motorists — and was hated immediately. I was right there with the rest. The new limits went into effect just as the ink was drying on my first driver's license.

The sale of radar detectors shot up and two-way CB radios began sprouting under truck and car dashboards as drivers tipped each other off about speed traps.

Sammy Hagar's popular "I Can't Drive 55" song in 1984 played to the contempt for forced conservation: "When I drive that slow, you know it's hard to steer. And I can't get my car out of second gear. What used to take two hours now takes all day. It took me 16 hours to get to L.A."

But still, the price of gas kept climbing. I remember taking a picture of the sign at a gas station on the south side of Chicago the day the price topped a buck a gallon in 1978.

But almost 20 years later a revolutionary thing happened: Restrictions came off in 1995, and the oversight of speed limits was returned to the states. A counterculture of speed demons started to give way to a subculture of conservationists now known as hypermilers.

Hypermilers, of their own accord, go to significant lengths to boost their vehicle's fuel economy by vigilantly changing air filters and keeping up on other routine maintenance to boost their car or truck's gas mileage. They start slower when traffic lights turn green and let off the gas and coast toward a stop, avoiding their brakes, as soon as they can see a red light coming.

Shutting the engine off at stop lights, planning routes with time-saving right turns instead of left turns across traffic — even keeping extra stuff, and weight, from accumulating in the trunk are among the techniques the conscious hypermiler has on his checklist.

Most of these techniques are not new by themselves but are trendy as a collective "thing." And they are popular because people want to do them — not because a government program is telling them to. There are hypermiling road rallys and websites abound with hypermiling tips.

That said, there are a few more extreme hypermiling techniques I wasn't sure about. I gave a laundry list of them to my friend Dwayne Baird, the spokesman for the Utah Department of Public Safety. He tried the ones that make sense and said his car's mileage computer gave him instant results that his gas mileage was improving.

The most interesting thing I confirmed is that the posted speed limit on the freeway isn't always the speed limit. If all of the cars around me on I-15 are going 80 in a 65 mph zone, and I drive 65, and it makes the other drivers pull around me, I could get a ticket. The flow of traffic trumps the sign. Anyone who has driven I-405 in Southern California at rush hour has seen bumper-to-bumper traffic doing Mach 1. Going slower would be a really bad idea.

But on a four-lane highway, I can go slower in the right lane if there is plenty of room for cars around me to pass on the left. Baird has an adviso: If a mix of speeds is present, a driver doing 80 is going to have a hard time convincing a trooper he was just going with the flow of traffic.

I asked Baird about a thing we used to call "drafting semis," which means driving behind big trucks so close that the truck pushes air out of the way, pulling along the car behind it. It's still an extreme hypermiling technique. Baird confirmed that what's now called "Rubbing is Racing" would be both a bad idea, and illegal, because the car trailing the semi would be following dangerously too close.

Turning off the engine? A great idea if the car is stopped. But people who do that while the vehicle is moving to save a little gas forget their power steering and brakes shut down when they do. And if the key gets turned a little too far in the off position — the steering wheel locks. "Very dangerous," Baird said, adding that troopers responding to a bad crash who find the ignition key turned off have to wonder what the driver was up to.

Over inflating tires boosts gas mileage, but that's also a bad idea. The practice can make tires overheat, which can make them explode, which at highway speeds can shoot the car out of control. "It takes all of that hypermiling effect, if you will, out of the equation if you have to buy a new vehicle," was Baird's understated response.

One final bit of encouragement takes the form of one of those math story problems junior high kids love so much: If driver X commutes 15 miles going 80 and driver Y commutes 15 miles going 60, how much extra time does it take driver Y to get to work?

Hypermilers say you'll be surprised how little time you'll lose going slower, all while spending less of your hard-earned cash at the gas station.

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