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When you accelerate, you’re converting electrical or chemical energy into kinetic energy, and adding that kinetic energy to your vehicle. Your vehicle and everything in it becomes a giant inertia “battery” that holds kinetic energy.

All of the metal, the plastic, all of your belongings, and even your body store that energy while you’re moving. When you release the gas pedal, your car keeps moving until the rolling resistance and aerodyamic resistance, plus gravity when going uphill, bleed the kinetic energy away.

When you use the brakes, that kinetic energy is removed from the car and changed into thermal energy. This heat then is dissipated away into the atmosphere.

Regenerative brakes take some of the kinetic energy and turn it back into electricity for the battery. However, regenerative braking is not perfect. There are losses to heat and losses when converting the electricity generated back into chemical energy in the battery (again, heat).

Avoid Braking

From previous lessons, we learned that it takes a lot of wasted energy just to get power to the wheels. This adds kinetic energy to the vehicle’s “battery”.

The best way to save fuel is to not throw any of this energy away if you can avoid it.

Coasting

When you’re driving, look ahead for reasons you might have to stop. Be proactive and release the gas pedal sooner. This allows you to stop adding more expensive energy to the car and use more of that energy coasting rather than throwing it away through hot brakes.

For cars with regenerative braking tied to the gas pedal, don’t release the pedal all the way to coast. Find the point where it’s not accelerating you and not braking you. You can also use your power (kW gauge) on some cars to keep it at zero, rather than negative numbers (regenerative).

While regenerative braking is better than regular braking, it’s still worse than not braking at all. You only capture a small portion of the energy back when you brake with regen, so you’re still better off to not put energy into the car’s kinetic “battery” that you’ll waste later.

Downshifting and Regen

For gas cars, also consider using light downshifting as you near a stop. This will keep most newer cars from putting any fuel in the engine until you are almost at a stop (fuel cutoff). This also negates any need for shutting an engine off during coasting as many hypermilers do.

For hybrids and electrics, it’s good to start with your regenerative braking as you approach a stop rather than using your traditional brakes. You might be able to stop solely on regen power if you plan ahead a bit, or for surprise stops, you might be able to only use traditional brakes at the end.

Cornering

When you need to turn a corner, slow down going into it as little as you safely can to conserve energy and avoid having to use energy to speed back up again after the turn.

Whatever you do, don’t be stupid and come to a near-stop before making the turn. Not only are you wasting energy, but you’re risking being rear-ended by other drivers.

Buy Energy When It’s Cheap, Sell When It’s Expensive

One of the best ways to illustrate this is with a roller coaster. A chain pulls the roller coaster up a hill, building its potential energy. As it drops down the hill, that potential gravity energy becomes kinetic energy, and the roller coaster keeps going despite not even having an engine of its own.

Potential gravity energy can do great things for your gas mileage on the downhill, but terrible things for you on the uphill. The absolute worst thing you can do is go too fast coming up to the top of the hill, brake down the steep hill, and gun the gas to go up the next hill. When you do that, you are wasting your energy (gas or electric) and wasting the free energy gravity could have given you on the downhill.

The best way to handle hills is to add kinetic energy to your car by gently speeding up on the downhill portions, because this uses less gas than it does going up. You might go slightly above the speed limit like most cars usually do, or slightly above the flow of traffic in other cases, to save up this free gravity energy in your kinetic “battery”. By doing this, you’re “buying cheap”.

When you reach the next level spot or uphill, coast for as long as you can and use that kinetic energy. Use your gas pedal again once you feel you are going too slow and need to maintain or add speed. When you do this, you’re spending the energy you saved up in your “battery” during the easy times instead of “buying” kinetic energy when it’s expensive. Doing this, you’re “selling when it’s expensive”.

Another way to express this is “buy low, sell high”, like a merchant would do.

Safety Tip

Your ability to increase speed going down and decrease it going up hills depends on traffic conditions, as discussed in an earlier lesson. Don’t vary your speed unless you can do it safely!

Pulse and Glide

(image from MetroMPG.com)

Gas engines are actually more efficient when they’re accelerating. I know this sounds backwards, but it’s true. They don’t get higher current MPG during acceleration, but they can create more kinetic energy per gallon during a “pulse” of acceleration.

This gives you another way to “buy low” and fill up your kinetic “battery” by adding speed, but only if you “glide” afterward for as long as you can. This technique works best on level ground, or close to level, unless you pulse on the downhills and glide up.

Steps to a successful “pulse and glide”

  • Choose an average speed you’d like to travel over time
  • “pulse” your vehicle to a speed above that speed at 80% throttle
  • “glide” the car in top gear with pedal released for gas/diesel. Release pedal to the point where the gas motor cuts off in a hybrid, but not so far that regenerative braking occurs.

Other things to consider

  • Pulse and glide has been shown to work in electric vehicles, but you have to be sure the car isn’t regenerating during the glide. This may require putting it in neutral.
  • You can only tell with the average MPG meter whether you’re getting better mileage, and only after several cycles. Adjust your technique as necessary to get your car to its potential with pulse and glide.

Example

If you wanted to travel down a lonely road going an average of 60 MPH in a 75 MPH zone, you’d start by pulsing up to 75-80 MPH. Then, stay in top gear for gas vehicles. Release the pedal completely for gas vehicles, and to the point where the motor turns off in a hybrid (but not to the point of any braking). Stay this way and slowly decelerate to 40 MPH. Pulse again to 75 or 80. Repeat the above steps.

After a few pulses, check your MPG and see how you did! If you aren’t getting results, reset your average MPG and try again with less pulse and more glide. Or try again with a more or less aggressive pulse. Check results again. You can pulse to 10 over your average speed and 10 under, 5 over and 5 under, or some mix.

You’ll find the right mix for your car with experimentation.

Pulse and Slow Burn

Another form of this is “pulse and slow burn”. You can do a pulse, and then apply very light throttle during the glide to get great mileage while decelerating more slowly than you would in a true glide. Every vehicle is a little different, so you’ll have to try this on your car and use the MPG gauge to see if it works.

For Toyota hybrids, some can enter a “super highway mode” that gets as good as 70-100 MPG during the slow burn. It’s tricky to get the mode available and keep it there, so you’ll need to google “super highway mode” to learn more.

Safety Tips

Your ability to pulse and glide depends on traffic conditions, as discussed in an earlier lesson. Don’t vary your speed in this way unless you can do it safely!

Some hypermilers shut off the engine in their non-hybrids during the “glide”. This is potentially dangerous because you might lose power steering and/or power brakes, making it tough to avoid an accident or stop quickly. They DO save gas this way, but I don’t recommend this method for safety reasons. If you want the engine to actually shut off, buying a hybrid is the best way to safely do this.

Work The Throttle

Be smooth. Think about eggs.

To get the best mileage, be smooth when you need to change the throttle position, including taking off from a stop. Don’t make any sudden moves. Imagine that there is an egg between your foot and the pedal, and that you don’t want to crack the egg.

Holding Constant Throttle

One very easy way to “buy low and sell high” is to pick a throttle position when driving on a flat area and stick with it when you hit hills. Hypermilers call this Driving With Load “DWL”. It’s really easy….until your foot gets tired of sitting in that one spot.

The vehicle will naturally go up in speed on downhills and down in speed on uphills. The downside is that if the hills are too steep, you’ll go beyond the speed limit, or go way too slow on uphill. Just use your judgment if you’re going to try this technique.

When a vehicle has enough low-end torque, you’d be surprised at how little throttle will hold a speed up a hill. By experimenting with this, you can watch your efficiency and see increased mileage as you learn how to best apply this method to your vehicle.

Constant Throttle Takeoff

You can save gas by holding a constant low throttle position at takeoff to minimize your cost of building initial energy up. Just give light throttle, slightly more than it takes to creep forward. When you get up to speed, give a slight release to hold that speed.

As usual, only do this when it’s safe and you’re not clogging up traffic.

Setting an Efficiency Target

Another method you can use to increase your mileage is to pick a target efficiency and stick with it (within reason, and safety).

If you find that on flat ground your car is getting a certain efficiency, like 42 MPG for gas, or 300 Wh/mi, as an example for electrics, at 60 MPH, try to keep at or above that efficiency when you hit terrain and hills.

This method can work in conjunction with “buy low, sell high”. When you hit a downhill, increase speed and store the energy as speed. When you hit the uphill, bleed off the speed and slow down even more to hit your target. Applying light throttle while climbing and allowing your speed to slip down can save gas.

The only real difference between this method and “buy low, sell high” is that you’re using your MPG gauge to guide your energy expenditures.

Safety Tip

Your ability to increase speed going down and decrease it going up hills depends on traffic conditions, as discussed in an earlier lesson. Don’t vary your speed unless you can do it safely!

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