First and foremost… some of the techniques I will post here are ILLEGAL. Use them at your own risk (I don’t and won’t). As always, consult your local laws and adjust your driving style accordingly (unless you just want to get tickets, jail time, killed or manslaughter charges).
Now, with that out of the way. The ultimate ticket to improving your gas mileage is having a manual transmission vehicle. There are several very important reasons to have a manual, even in this modern era.
The first is, except for a few rare (and expensive) exceptions, you will always get more gears in a manual than an automatic. Most cars under about $35,000 still only have a four gear transmission. With a manual, you get five gears and can probably get six gears in anything (well, modern cars).
This is important for two reasons, the first is that the six gear (or fifth gear) will probably be an overdrive gear. That means that it’s a really tall gear. And that means that your engine can run slower for a given speed. Your acceleration will suck, but that’s why you have a manual, drop to fourth and hit the gas. But a slower engine at freeway speeds will result in higher gas mileage.
The other possibility is that your gears in the manual will be closer in ratio to each other than in a four speed automatic. Your engine has a very narrow range where it is really efficient (especially if it’s a little 4-cylinder engine). The ability to keep the engine in that efficient area means less gas results in greater acceleration and speed.
Plus, and this is big advantage to some people, you can effectively not use the engine. Push the clutch in and you’re coasting. The engine is idling and, if you are going down a hill, you can maintain speed and even speed up a little bit without using the engine at all. I admit that this only works well in hilly areas, your improvements may vary.
The exception to the automatic rules is the Continuously Variable Transmission. I’m not totally sold on them, but the are impressively efficient. Because, the computer puts the engine at it’s most efficient speed and then changes the transmission to increase the speed of the car. It’s a really neat idea, though it bothers some people, because the car “Just don’t sound right.”
OK, with that out of the way, let’s talk about other hypermiling tricks… and I’ll note the ones that are illegal… for my area. Your area may be different.
1) Drafting (illegal) – drafting is when you get right behind a much larger vehicle. Your car is in something of a wind dead zone and it’s not having to push its way through the air. The large vehicle in front of you is doing that for you. So you get a big bonus to mileage by running the engine slower for a given speed. The main disadvantage is that if the vehicle in front you slows down quickly, then you are going to hit it. CONTROLLED tests indicate a large gain (up to 39%) can be made… but that’s insane.
2) Slow Acceleration – Simply accelerating more slowly can get you pretty big gains. In a manual you control when the car shifts. You want to shift into a higher gear as soon as the engine can handle the load at the new speed. For most 4-cylinder cars, this will be about 1700-2000 RPM (you do have a tachometer right?). A larger engine will allow you to shift sooner. Shift out of first as soon as the car is moving forward. Accelerate slowly. This is my main technique for in town driving and I get about a 15% gain in MPG.
3) Coasting – as mentioned before, use the clutch, let the engine idle while rolling forward. This is useful when you see a red light or a stop sign up ahead. Provided that the cars behind you let you get away with it. I wouldn’t do this in rush hour. On the other hand, it’s a good method. Also is really good for hills. BTW: Be sure to take the car out of gear and release the clutch to keep from wearing it out.
4) Rolling Stops (illegal) – coming to a dead stop and then accelerating wastes a lot of fuel. Unfortunately, the rolling stop is illegal and extremely dangerous. I wouldn’t do this for any reason. What is legal is timing the stop lights along your route. With a little effort, you can figure out how to hit every light green.
5) Vehicle maintenance – check your tire pressure and add a little bit. You’ll wear out the tires slightly faster, but you’ll get a small gain in mileage because of less resistance and friction. Although, just keeping your tire at the recommended pressure will help. Also keep your oil changed, keep your air filter clean, and all that good stuff will help your mileage as well. Here’s some other good ideas. It’s also a good idea, especially for highway travel to remove roof racks. If you’re in town a lot, make sure your car isn’t toting around a lot of extra weight, you really don’t need that 500 mechanics tool kit in your trunk all the time.
6) Windows vs. AC – The mythbusters tested this. What they found was at speeds less than 50 miles per hour, you should turn off the AC and roll down the windows to save gas. At highway speeds, the additional friction due to down windows is higher than the AC use, so roll them up and turn on the AC.
7) Speed limits – do them
8) Think ahead – nothing kills mileage more than having to slam to a stop from 45 miles per hour, then get back up to speed quickly. Watch what other cars way ahead are doing and be prepared to slow down earlier instead of braking at the last minute.