Maximize Your Car's Efficiency With 'Hypermiling'

by David DeFranza on 16 January 2008 19 comments
Photo: edkohler

By now you have probably heard of hypermiling and the 50-90 mpg exploits of Wayne Gerdes . If you haven't, hypermiling is a set of techniques and practices that seek to maximize a vehicle's fuel efficiency through careful and calculated driving.

What this means to the average motorist is that you must alternate between driving like my grandmother and bracing against the g-forces as you take turns and exit ramps at 50 miles per hour. Of course, this is the extreme example of what hypermiling is and can achieve. The truth of the matter is that a few simple practices can dramatically improve your car's efficiency.

Here are a few things we all could learn from hypermiling:

Keep a record of your gas millage. By using your odometer to track miles per tank, you can develop a sense of your car's consumption over time and adjust accordingly.

Take note of your own driving habits. The fundamental principle of hypermiling is to use all of your car's energy to generate forward momentum. By leaving ample space between yourself and the car in front of you, there is enough time to coast to a stop and avoid stepping on the brakes.

Avoid standing still with the engine running. Traffic lights are the biggest cause of this. If you see a red light in front of you, take your foot off the gas and let your car coast up to it. Sitting in traffic should also be avoided. Though a very advanced technique, hypermilers practice riding the "waves and jams" caused by congestion to minimize time accelerating, decelerating, and sitting stopped.

Accelerate gradually, over a greater distance. The longer your take to achieve a speed, the less fuel it will require to get there. In many cars, using cruise control to slowly approach the desired speed will help regulate accelerations.

If you have tried these basics you may be ready to take a shot at the big efficiency numbers. For this, you will need more advanced hypermiling techniques which, while controversial , may help eek a few more miles out of every gallon. These include:

  • Over inflating your tires, which reduces the amount of rubber on the road, and thus, reduces the resistance on you car. However, because it can also lead to a loss of control, uneven tire wear, and blowouts, it is not for the hypermiling neophyte.
  • Riding the white line keeps your car out of puddles and grooves in the road made by other drivers, both of which increase drag and decrease efficiency.
  • Rolling up the windows and turning off the air conditioning maximizes your car's wind resistance. A bottle of ice water on a hot day can make this more manageable.
  • Finally, by keeping up with regular maintenance and stripping your car of unnecessary weight, like roof racks and miscellaneous odds and ends collected in the trunk, you can help keep your car at its engineered efficiency years after it has left the factory.

Hypermiling may not be for everyone, but if you are planning a road trip or have a long daily commute these techniques can drastically improve your cars efficiency. Besides that, they add a fun new challenge to driving that can save you money.

For more information on hypermiling, its history, and even more advanced techniques, check out the sites below:

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Guest's picture
Bean

I remember first hearing about the hyper-miling thing and being appalled. That guy uses techniques that make him a danger to himself and everyone else on the road.

Some of these bits of advice are good (don't start & stop too quick, leave yourself plenty of room, etc), but that guy just takes it way WAY too far.

Guest's picture
Guest

Hey guys,
Here is a great book to help you distinguish the differences between safe and dangerous hypermiling techniques.

http://hypermilingbook.com/"

Guest's picture
Aryn

They had a profile of him a few years ago. One thing the reporter noted was that many of his practices, like turning your engine off at red lights, are illegal in some states. Check local laws before you try it!

Myscha Theriault's picture

Welcome to Wise Bread, David!

David DeFranza's picture

I certainly agree that those truly dedicated to hypermiling become a bit self-centered in their practices.

Safety first!

Thanks for the welcome Myscha.

Guest's picture

Apparently a modern (electronically controlled injection) engine is always less efficient on acceleration than on a steady speed. Consequently you should reduce time spent accelerating. Accelerate as quickly as you with retained control, safety and comfort cant, up to your desired speed, then shift to the highest gear reasonable for that speed, or let your automatic transmission set into as high gear as possible. Of course some automatic transmissions may think that your fast acceleration up to the desired speed means that you want to drive sportily, and thus they may set into a lower gear than necessary to give you more available power.
Also, when travelling up hill, allow the car to loose speed, when travelling downhill regain that speed by allowing the car to coast up to and beyond the set speed limit (but not too far beyond, beware of smnokey bears) and then to coast down to the speed limit on the plains.

Guest's picture
Raymond Fowler

This advice is way off base. Max economy is obtained by accelerating slowly to speed not as fast as the thing will get to speed.
My credentials are a Master's Degree in Mechanical Engineering.

David DeFranza's picture

Excellent advice Sprithitler. Many people use cruise control for acceleration because, in many newer cars, it is the most even, steady means of speeding up.

I also couldn't agree more with your advice on tackling hills.

Many cars with automatic transmission have a 'sport' button, or something like it. This essentially tells the car to stay in a low gear longer, as doing this does indeed increase speed at acceleration. If you want to save gas, be sure this feature is switched 'off.'

Guest's picture
Guest

My 14 mpg Jeep TJ salutes this article.

I need your gas.

I'll drink it up!

Guest's picture
Guest

If you plop yourself in neutral going down a hill, you free up the engine, and you freely roll down, bringing the rpms down, and not holding back the speed with the engine against you.

Guest's picture
Zeke Kossover

Two points:

1. Over-inflating tires. This does reduce the energy necessary to making the car go, but not because less of the tire is touching the ground. You want the tire to have good contact with the ground and lots of friction because only through friction with the ground can the car push on the road to speed the car up. Imagine if the car were on frictionless ice, you'd never get it moving.

Over-inflating the tires helps because it makes the tire stiffer. It is the flexing and changing of the shape of the tires as it turns that eats up energy from the moving car. You can understand what is happening by thinking about a rolling bowling ball and balloon filled with sand. The bowling ball barely changes shape as it moves while a balloon filled with sand has lots of internal parts that are changing shape. So, the bowling ball will roll for a longer time starting from the same speed as a balloon filled with sand.

2. The situation with slowing down is more complicated than presented. It takes energy to get a car moving. To some degree, it doesn't matter how fast you get up to speed, it's the top speed that matters most. However, your car is more efficient in higher gears and you cannot get into a higher gear if you are accelerating hard. Thus, it is to your advantage to accelerate slowly.

Slowing down doesn't really cost you fuel directly. Unless you are driving a hybrid, your brakes just throw away your energy of motion. So, slowing down unnecessarily costs you since you will need to speed up again.

The final complicating factor is wind resistance. The internal friction of your car is pretty small. If there were now wind resistance, you could get close to just turning your engine off and gliding once you reached cruising speed. However, wind resistance means that the engine has to expend energy even at speed. Worse, the wind resistance increases with the square of your speed, meaning that going twice as fast costs you four times the energy which has to come from the gas. At 50 mi/hr, you have just about half the total wind resistance of 70 mi/hr. This is a huge savings. So, in general, the more time you can spend at lower speeds, the more energy you will save.

Thus, it is not to your advantage to rush between lights since that top speed will cost you all over the place and will barely get you there faster.

3. Going into neutral is generally not that helpful. Most hills (well at least in the Bay Area) will get you going really fast -- faster than you'd want to go. To that extent, it is usually good to let the engine help you brake.

Guest's picture
Ryan

er - "Rolling up the windows and turning off the air conditioning MINIMIZES your car's wind resistance." not maximizes...

Guest's picture
donee

Hi All,

Acellerating is not simple.

Most cars (Prius for example not included in this) have what is called Enrichment. The quicker the peddle is depressed, the larger an extra squirt of gasoline is made. If you ever rebuilt an automotive carboratuer, one is instructed to test this socalled "enrichment circuit" by flipping the trottle bar quickly and observe the squirt of gas out of the enrichment squirts, which normally send no gas to the engine. In Fuel Injected cars, the computer does this.

This is the source of the truthful "acellerate gently to save gas" recommendation.

On the other hand, there is engine efficiency versus power. Engine efficiency is very poor at low power for two reasons. The internal aerodynamic design of the engine (valve size, overlap, manifold runner sizes) and while at low power the engine is working hard to pull air past the part open throttle. To get best efficiency, you want the throttle full open, but the engine loaded so it does not rev high. This almost impossible to do in an automatic transmission car, but in a manual, one can modify the shift points to get better fuel economy.

But whatever you do, do not press the peddle down quickly. Ease it down gently, to avoid the enrichment action. Depending on the car and the shift points, reasonably quick, or dog slow aceleration can result. But your not going to win any drag races doing this.

Guest's picture

Attended a "dream-machines" combination air-show/car-show/boat show a few weeks ago... and a bunch of alternate fuel vehicles were on display--I was inspired to create a Squidoo lens ( www.squidoo.com/alternate-vehicle ) on Alternate Fuel Vehicles (and of course, the Honda Civic and the Toyota Prius are main features!). Hypermiling is a great way to rethink fuel economies--however, our politicians and automakers must do their part in improving fuel-efficiency of all new vehicles and providing those that use something other than petroleum-based fuels Websites like yours are a great start to get folks thinking about alternatives available to them--keep up the good work.

Guest's picture
JIMED

WE MOST DEFINITLEY NEED TO EXPLORE ALTERNATE FUEL SOURCES, BUT ETHANOL IS NOT THE ANSWER! JUST LOOK AT THE PRICES OF DAIRY,MEAT,AND ALL THE FOOD PRODUCTS. THIS MOVE BY THE FEDS WAS A KNEE-JERK REACTION TO APPEASE A SMALL GRUOP OF THE UN/UNDERINFORMED POPULACE. WHAT HAPPRNS IF OUR NATION'S CORN PRODUCERS CAN'T THEIR CROPS PLANTED ON TIME OR WE HAVE A NATURAL DISASTER? ARE WE THEN LOOKING AT $5.00/GALLON FOR GAS AND MILK? WE HAVE THE CRUDE RIGHT HERE AND KNOW HOW TO GO GET IT WITH ALMOST NO IMPACT ON THE ENVIRONMENT, AND THE AUTO MAKERS ARE COSTANTLY WORKING ON IMPROVING FUEL ECONOMY. IN THE MEAN TIME, LET'S ALL GET INTO THIS HYPERMILING THING!

Guest's picture
Mal

Modern ECU's (engine control units) use the logic of fuel cutoff during deceleration with the engine. This means that it is actually more fuel efficient to use the engine for deceleration rather than selecting neutral and coasting. The trick, of course, is to evaluate/regulate the amount of deceleration that is required.

The light ahead is red, you judge that you can come totally off the accelerator and engine brake without additional braking until the light turns green or you must stop using minimum brake. This results in a much more efficient deceleration than would neutral, coast and brake as required. The fuel used in maintaining idle RPM would be saved.

Even more savings could be realized by coasting from a further distance with the engine shut down but the loss of power assist to steering and brakes compromises safety to the point that it is probably not worthwhile.

Acceleration is always a compromise. Accelerate too hard and friction losses are excessive. Accelerate too slowly and pumping losses are excessive. Probably best is brisk acceleration with shifts keeping RPM low and the throttle fairly open; even to the point of short shifting ie. 1st directly to 3rd to 5th.

This principle of large throttle opening at low RPM was the principle that allowed John Wayne and Robert Stack to make it to SFO.........

Guest's picture
scott

I consistently get 40 mpg in my 96 corolla 5 speed - easy - could do better if i slowed down an drove the speed limit but even half assed it is easy

tire inflation high but not way high
Coast whenever possible- keeping RPM's down - (idles at 800-900)
try not to brake
accelerate slowly - shift quickly into high gear

the rest is anticipation
i rarely use cruise because a lot of times on the hwy I can coast

Guest's picture
Frank

It's amazing how much more gas per gallon you can achieve just by changing a simple "but often" neglected Airfilter.

Hypermiling your Car

Guest's picture
Diana P

Hypermilers are hyper ANNOYING. Sorry that you want to keep 6 car lengths ahead of you empty at all times so you never have to apply your brake, but you're a slow-moving hazard and some of us would actually like to reach our destination someday.