Tuesday, July 8, 2008

Stretch Your Gas Dollar with “Hypermiling”

You know how those EPA fuel economy estimates usually oversell? Well, some people manage to exceed those values, just by modifying their driving habits.

The practice is called hypermiling.

“The terms "hypermiler" and "hypermiling" originated in the online communities of Clean MPG, which is devoted to raising fuel economy and lowering emissions,” writes Nate Chapnick in edmunds.com.

“The actual practice of hypermiling likely dates back to World War II gas rationing; in fact, during the fuel crisis of the 1970s, Reader's Digest published a guide for consumers that included many techniques now commonly used in hypermiling. Today, however, hypermilers are not only more serious about their craft; they also rely heavily on new technology to achieve such astounding fuel economy.”

How astounding?

Try 52 miles per gallon with a Toyota Corolla.

Try 75.6 miles per gallon with a 2001 Honda Insight. (Source)

Bear in mind the typical mileage you get from these cars: according to the US Department of Energy, the 2008 Corolla’s fuel economy is 29 mpg, city and highway combined, and the 2001 Insight is rated 48 mpg in the city, 60 on the highway. (Source: www.fueleconomy.gov).

So how do we squeeze that sort of mileage out of a gallon of gas?

Whether we choose to follow them or not, most of use know the basic hypermiling techniques.

Maintaining an efficient speed is an important factor in fuel efficiency. The optimum speed varies with the type of vehicle, although it is usually reported to be in the range of 35 to 55 mph. For instance a 2004 Chevrolet Impala had an optimum at 42 mph, and was within 15% of that from 29 to 57 mph. (Source)We know that the faster we drive, the lower the fuel efficiency – yet how often do you drive at the speed limit, only to be passed by vehicle after vehicle roaring by at 75 mph, drivers flashing you surly looks? (They ought to look surly – think about how much extra gas they’re burning!)

The national speed limit could drop back down to 55 mph, though. Senator John Warner (R-Virginia) asked Energy Secretary Samuel Bodman to look into what speed limit would provide optimum gasoline efficiency given current technology. He said he wants to know if the administration might support efforts in Congress to require a lower speed limit. (more)

Here's a rule of thumb: If you're in a drive-through restaurant/business line or waiting for someone and you'll be parked and sitting for 10 seconds or longer... turn off your car's engine. Why?? For every two minutes a car is idling, it uses about the same amount of fuel it takes to go about one mile. Today's cars use electronic fuel injectors, which rigorously control the amount of gas delivered to the engine when you hit the ignition. As a result, virtually no fuel is wasted during startup, and only a thimbleful is burned as the car roars to life.

Research indicates that the average person idles their car five to 10 minutes a day. People usually idle their cars more in the winter than in the summer. But even in winter, you don't need to let your car sit and idle for five minutes to "warm it up" when 30 seconds will do just fine. (More)


Accelerate slowly over the longest possible distance. The slower you accelerate, the more you extend it over time and the less gas you use.

Go easy on the brakes - you used gas to move, but when you brake you're turning that motion (and the money spent on the gas) - into heat. Therefore, the more you move without braking, the less energy wasted.

MORE TIPS from the edmunds.com article on hypermiling. Note that some of the techniques could compromise safety.

Overinflate tires
Larry Singleton, a systems analyst in Phoenix and the owner of a 2007 Toyota Camry Hybrid, overinflates his tires by about 15-20 pounds. "I consider it safe because most of my driving is around town and under 50 miles per hour," said Singleton. According to Singleton, putting less rubber on the road gives him an edge in beating the EPA's rating by decreasing rolling resistance. However, such a practice could lead to uneven tire wear or worse, a loss of vehicle control.

Watch the real-time mileage display
Some vehicles are equipped with readouts that compute your real-time fuel use on a miles-per-gallon basis. Singleton watches the onboard display and adjusts his throttle inputs based on the readout to maximize his fuel economy.

Pay attention to wind conditions
James Cullen, a retired locomotive engineer and Toyota Prius owner, has found that his fuel mileage is significantly impacted by favorable wind conditions. "On long highway rides, having a tailwind has made a big difference in my fuel economy." If you know it's a windy day and you don't have to take that trip, then don't," said Cullen.

Place cardboard over the radiator
Chuck Thomas said that a cold engine reduces fuel-efficiency. How can you warm up the engine faster? Office Depot's silver-colored cardboard. Yes, that's right, cardboard. Thomas covers his radiator with cardboard to block the wind, thus retaining heat and keeping the engine running at a warmer temperature. Cautioning about the risk of overheating, Thomas said, "I'll take off the piece of cardboard if I know that I'll be driving a long distance, say 100 miles, but it's fine for my daily commute."

Of course, a cold engine's thermostat already remains closed until the engine is warm, so the cardboard isn't necessarily really helping it warm up faster but it will make the car's engine run at a higher operating temperature. In cold climates this might promote better fuel economy.

Minimize stoplights and stop signs on your route
Before leaving for an unfamiliar location, James Cullen maps out his route to ensure that his pathway has the fewest stops. "Every time you stop and start, you waste fuel. So it's easy to go on the Internet and map out a route with fewer stoplights and stop signs," said Cullen. If you can't avoid the stoplights, determine the optimal speed for the timing of the stoplights. "Taking this small step has a marked effect on your fuel economy," said Thomas.

Ride the ridge
Riding along the painted white line used to be reserved for road bikers looking for a surface with less friction. Friction decreases your fuel economy by adding drag to the vehicle. However, hypermilers now use this white line to increase their fuel economy, a tactic that's especially useful in the rain when puddles form in the grooves of the road, which significantly increases rolling resistance.

Run without the A/C and keep windows closed
This tip could have you sweating bullets, but just think about all the water weight you'll lose. Alison McKellar of DeLand, Florida, recently purchased a new Prius. McKellar quickly became interested in conserving fuel and said she "found the strategy on a site for Prius owners. I realize substantial fuel economy gains by not running the A/C, so before I head out for a trip, I make sure to bring plenty of ice water to stay hydrated," said McKellar.

Baby the brakes while being "surroundings aware"
With this technique, hypermilers treat stop signs as though they are yield signs — and slowly glide through. Cullen, a Prius owner, said, "If I see no one is there [at the stop sign], then I just roll through it, which keeps the car in electric mode." This technique is especially important for non-hybrid hypermilers, whose vehicles do not feature regenerative braking, a technology that recharges the hybrid's battery, which runs the electric motor.

Driving as if you don't have brakes requires constant anticipation and planning, dubbed "surroundings aware," which hypermiler advocates say promotes defensive driving. But the technique may sometimes require hypermilers to tailgate or take corners at speeds that aren't truly safe, all in the hopes of never touching their brake pedals.

Keep up with maintenance
Even non-hypermilers will find this tactic easy to follow. Keeping your vehicle properly maintained by changing the air filter and oil according to the manufacturer's scheduled tune-ups will have a positive effect on your fuel economy. Hypermilers also recommend regular balancing and aligning of your tires.

Get rid of what you don't need
Hypermilers always travel with the bare essentials. Chuck Thomas said that he never "leaves junk that I don't need in the trunk." He also recommends removing the roof rack when not in use, as it creates unnecessary drag on your vehicle. "The more drag on your vehicle and the heavier it is, the worse mileage you'll get," according to Thomas.

"Potential parking" and "face-out"
According to Wayne Gerdes, winner of the 2006 Hybridfest MPG Challenge, "Park at the highest spot in the parking lot and face out." This technique allows you to exit by rolling forward in neutral without turning on the engine, thereby saving gas. The technique does away with the backing up and braking required by nose-in parking, while also reducing the time the engine runs. This strategy is easiest to use where there's at least one corner of the lot without other parked cars.

"Pulse and glide"
This is perhaps the most complicated technique employed by hypermilers. On a Prius, the optimal speed for this tactic is around 30-40 mph, said Prius owner Cullen. The first step in the pulse-and-glide technique is to pulse, which is to accelerate the vehicle to around 30 or 40 mph. In the Prius, once the speed has reached 40 mph, ease slightly back on the accelerator until no energy arrows appear on the energy monitor, indicating that the vehicle is neither relying on the engine nor recharging the battery. As a result, the car begins to glide. When the vehicle slows to about 30 mph, repeat the whole process again, pulsing and then gliding.

The pulse-and-glide technique improves fuel economy by minimizing use of the internal combustion engine. There is a version of this technique that can also be applied to non-hybrid vehicles, but be aware that it is outlawed in several states because it would require actually turning the engine off, which causes the power-assist for the brakes and steering to fail. If the key is in the off position, the steering will also lock.

Coaxing an "auto-stop"
Similar to the pulse and glide, auto-stop simply involves placing the vehicle's transmission into neutral, turning off the engine and coasting to a stop. This seems innocent enough, but any time a car is moving without the engine running, vehicle control is compromised. Some devoted — and dangerous — hypermilers do this while driving down a hill at rather high speeds, refusing to brake even around corners. Some people might even call this technique irresponsible.

Draft at your own risk
A "draft-assisted" auto-stop involves tailgating a semitruck. By taking advantage of the draft generated in the truck's wake, wind resistance is markedly reduced for the hypermiler's car. "This is particularly dangerous," said Thomas, "as you must travel dangerously close to the 18-wheelers for the technique's full effect."

Read the whole article at edmunds.com.

Regarding drafting: Discovery Channel's Mythbusters, in their June 6, 2007, episode, took a series of measurements where they drove a Dodge Magnum Station Wagon at 55 mph right behind a Freightliner tractor trailer. As they got closer their results ranged from a baseline (no truck) figure of 32 mpg, to 35.5 mpg (11 percent improvement) at 100 feet, and then progressively up to 44.5 mpg (a 39 percent increase) at ten feet, as a result of decreased drag consequent of drafting. They strongly emphasized that drafting a big rig at such close distances is life-threatening and extremely dangerous. They recommended a minimum safe driving distance from a big rig is 150 ft. (source)

For hypermilers, the task of improving their fuel economy is an entertaining game, albeit a serious one. Every drive for this elite group of fuel-sippers is an opportunity to break their own mileage record. They may never stop — literally — in their quest for ultimate fuel-efficiency.


More hypermiling and fuel-saving articles:

First, meet the Grandaddy of Hypermiling, Wayne Gerdes:
This Guy Can Get 59 MPG in a Plain Old Accord. Beat That, Punk. (Mother Jones) Here's another article on Gerdes from CNN.

How to Increase Your Gas Mileage (Washington Post)

Is an Idle Car the Devil's Workshop? (Slate)

Does it Really Save Gas to Roll Down Your Windows Instead of Flipping on the AC? (Slate)

Dallas hypermiler Chuck Thomas demonstrates his techniques (Video, Dallas Morning News)

Fuel economy-maximizing behaviors (Wikipedia)

Note that the Automobile Association of America says hypermiling is dangerous when taken to the extreme.(Article)

Read the rebuttal from hypermilers at Cleanmpg.com.