The problem isn’t with vehicle technology; it’s that wind resistance increases with increasing speed, and the increase isn’t linear: the faster you go, the more the resistance increases. The savings are particularly significant if you’re up here in Canada, where fuel prices are up to twice the U.S. cost (depending on the exchange rate at any given time).

It’s also worth noting that you’re also cutting greenhouse gas emissions significantly. That’s also compelling. Ditto for the fact that the slower you’re driving, the more likely you are to survive an accident, avoid driving off the road if you hit a patch of ice (a concern at this time of year), or avoid an animal that runs out in front of you. Also not a negligible benefit.

It’s true you shouldn’t drive excessively slower than the rest of traffic, but if you’re driving slow in the slow lane, people coming up fast from behind can simply go around you. If they can’t figure out how to do that, they shouldn’t be driving.

On another note, maintaining a constant speed is another huge fuel saver. The more often you have to accelerate back up to speed, and the harder you accelerate, the more fuel you waste. Keeping a safe following distance lets you reduce the frequency of braking hard and having to accelerate back to speed.

What I do when I go 55 is use my hazard flashers generously. When I see someone even far behind me in the (right lane, of course), I put them on. This alerts the jackasses who are on the phone or listening intently to interesting entertainment rather than paying attention to the fact that they are behind the wheel of a moving vehicle that I am going slower than they are.

No crashes, no near-misses, and I don’t cause crashes. But then, when I drive, I DRIVE.

Jonathan, I found someones test results for a 2008 Corvette and the max MPG was around 35-40MPH. Course thats just one data point.

The benefit doesn’t come just from where the car’s engines runs most efficiently. It may be that newer cars run more efficiently at a slightly higher RPM, or that the gearing has changed to allow them to go faster at the optimum RPM. The differences at high speeds is related to drag. As speeds increase it requires more energy to overcome the effects of drag. In other words, it takes more gas to drive 65 mph instead of 64 mph than the difference between driving 35 mph and 34 mph. 55 mph seems to be the sweet spot for most cars, but there are exceptions. I have seen anecdotal evidence that a Corvette gets almost the same fuel economy at 55 mph vs 75 mph. This is, of course, a car that is built for speed and is more aerodynamic than most passenger cars.

If you drove 60 hours you would have saved $10.40.

Or perhaps for every 60 hours of similar driving….

In terms of safety, it’s the difference between the speeds of the individual cars that makes the biggest difference. One car going 64 and while the rest average 65 isn’t going to matter than greatly, but one car going 55 while the rest average 65 is taking a risk.

Word of advice. If you’re going to drive on the interstate, stay in the right lane, and stay out of my way! I have places to be, and after a couple thousand miles of interstate, I’m sick of looking at it.

AnnJo- yes, using the break is literally throwing away gas. The gas creates momentum, and using the break throws away that momentum, or a significant portion of it. When I am driving around town, if no one else is behind me, I will let my car naturally decelerate to stop signs and red lights. I also coast down hills. Boosted my MPG from 28 to 33.

Though some of the practices are unsafe, you can google hypermiling.