Thursday, December 20, 2012

Hypermiling, the basic techniques

Driving to visit relatives this Christmas? Try hypermiling: getting the most possible miles per gallon out of your car.

Streamline the car: Windows up, tires inflated to the manufacturer's recommendations or slightly higher, unused trunk or roof racks removed, excess cargo removed. Like, do you really need to haul your golf clubs in your trunk all the time?

On the highway, find your car's natural cruising speed and stick to it; likely it's around the highway speed limit, 55-60 MPH. Pay attention to your RPMs at different speeds, and you'll see where the engine seems to settle in. If you have a newer car with an actual MPG readout, it's even easier to see at what speed your car runs most efficiently. True, it will now take more time to get from A to B than if you were driving 75, but you will have used noticeably less gas. I can attest to that after our many road trips between Chicago and St. Louis.

Also on the highway, you can reduce the air resistance on your car by drafting behind a large truck. It's not a safe technique, because you have to follow the truck closely, and the truck drivers don't like it—probably for that reason—but we've done it. Again, if you have a car with an instant MPG readout, you could try it and see the difference. But beware: it is unsafe, you will have no way to see what's coming ahead, and it's probably illegal. I'm just saying it works.

Conserve momentum #1: Keep plenty of space between you and the vehicle in front of you, even more than the recommended one car length for every 10 miles per hour. The extra space will allow you to coast a bit before braking—if you even have to brake at all—as the flow of traffic changes. Give yourself enough space in slow-moving traffic, and you may be able to simply roll along the whole time without ever hitting the accelerator.

Conserve momentum #2: Coast to stop signs and red lights. For some reason this annoys other drivers, like they're in a real hurry to get to that red light. So what? It uses far less fuel than keeping your foot on the gas until the moment you have to slam on the brakes while also preventing fender benders caused by people having to slam on their brakes at stop lights. If the light turns green while you're coasting toward it, even better; you won't have to accelerate as much to get back up to cruising speed. At stop signs, if you can continue rolling until the car before you departs the stop sign, then you're right there to stop for a moment and go, avoiding the stop, roll, stop, roll, stop.

Shut your engine off at any stop more than 20 seconds. Unless you really have to worry about whether your car will start again, there aren't many good reasons to keep the engine running when you're not actually driving. Deny it all you want, prolonged idling does indeed use more fuel than turning the car back on, and by "prolonged" I mean about 20 seconds or more. This is such an easy, no-effort, no-brainer way to conserve fuel at railroad crossings, stop lights with an obvious rotation, drive-up ATMs and slow-moving drive-throughs, not to mention the times you're waiting in the car while your buddy runs into the store. And when you're about to leave a parking space, wait to turn the engine on until you are actually ready to move.

Advanced technique: Engine-Off Coasting. In other words, consider coasting to be another form of idling. Yes, I am suggesting you take your foot of the gas, put your car in neutral, and kill the engine. You do this by turning your key just enough to shut the engine off and then turning it back to the "run" position. You know, the key position just before you'd click it over to turn the engine back on. And just roll. We are mimicking the engine-off coasting of a hybrid vehicle.
BUT: For goodness sake, don't turn the car all the way off—you'll lock up the steering! Also, while we frequently employ this method in our automatic-transmission, power-steering car, you should understand that it is really best suited to vehicles with manual steering and a manual transmission. You can lose power steering when the engine is off, making it very tough (but not impossible) to turn the wheel, and the jumping between drive and neutral and back while the car is in motion may damage automatic transmissions. 
 On a hill, gravity will take you. On a flat or uphill surface approaching a stop, the friction will gradually slow you down. When it's time to hit the accelerator again, first turn the engine back on, then pop the car in drive and go. Obviously, traffic conditions must help you determine if engine-off coasting is appropriate, but in general, according to an forum, the hierarchy of slowing/braking techniques from best to worst is:
     1) coasting in neutral, engine off (i.e., roll to a stop);
     2) coasting in neutral, engine idling;
     3) regenerative coasting (hybrid vehicles)
     4) regenerative braking (hybrid vehicles)
     5) coasting in "deceleration fuel cut-off" mode (in gear, above a certain engine RPM)
     6) conventional friction braking (non-hybrid or hybrid)

There are quite a number of other hypermiling tactics that you can find with an online search. Determine what's compatible with your vehicle and your route (e.g., city-driving methods vs. highway driving methods) and try it.

Make it game! Track your fuel efficiency—either by watching your car's MPG readout, or by the old-fashioned way of writing down your odometer's reading and the number of gallons you put in every time you fill up and then doing the math—and see if, with every trip, you can't get your miles per gallon higher and higher and higher...

Shared at the Preparedness Fair 


  1. Wait...don't you want your miles per gallon to be higher and higher...more miles to the gallon?

  2. Whoops, yes. I guess I was thinking in terms of fuel usage being lower... Corrected!

  3. mind is warped from too much math. Computing math while drafting illegally. Even worse! LOL Just be safe. I'm ALMOST surprised that you are not advocating bike riding or walking ALL the way to St. Louis.
    Jingle Jingle !
    Love from the Allen family