Introduction to Hypermiling
A canned post by theholycow
Originally posted at
http://www.gassavers.org/showthread.php?t=7781
Please include the link if you post/distribute this elsewhere.
This is a first draft. Feel free to critique it. I was thinking about putting something together for new users who ask how to get started, as I feel the existing documentation is a bit sparse; and my parents started asking about it, so I decided to go ahead and write it and let everybody benefit.
I think I need to re-order the points. Tire pressure, antenna removal, and racks should probably be together.
Contents:
Introduction - basic strategies that you already know, but should review
Basic:
1. Proper maintenance
2. Increase tire pressure
3. Drive slower
4. Eliminate unnnecessary idling
5. Drive as if you have no brakes and no accelerator - look far ahead and eliminate braking/accelerating
6. Use open windows or air conditioning at the right times
7. Put your automatic in "N" when stopped instead of leaving it in "D"
8. Use neutral when coasting, braking, or slowing
9. Shift at lower RPM if possible
10. Drive off-center
11. Limit accessory usage
12. Use the correct fuel
13. Remove unused roof racks
14. Remove or relocate your radio antenna
15. Use a MPG or fuel rate display
16. Cruise smoothly in stop-and-go traffic with a long following distance
Advanced:
17. Drafting large trucks with safe following distance
18. Study actual fuel usage rate in realtime
19. Pulse & Glide
20. Engine-off coasting
21. Vehicle modifications
Introduction:
Hypermiling is the art and science of exceeding the EPA's fuel economy estimates and continuing to improve. Even if you don't care to beat the EPA, you can still learn some strategies that can help, and you may have some fun too.
Of course you know that the best way to save gas is to avoid driving. Consolidate errands into one trip (and go to the furthest one first, that way the engine is fully warmed up for all the errands). Carpool. Walk or bicycle to close destinations. Don't circle the parking lot for five minutes like a vulture trying to find a good space; take a far space, get some exercise walking (which is still faster than finding a close space), and enjoy the fact that you're less likely to get your door dinged.
You probably also know the most reasonably accurate way to calculate your average MPG. You should do it even if you have a gauge that shows MPG, so you can make sure it's accurate. Every time you fill your gas tank, reset your trip odometer. Then, the next time, divide miles from the trip odometer by gallons from the pump. For this to work accurately, fill at the same pump every time, and stop filling after it clicks once. I like to write miles and calculated average MPG (along with whatever fuel-saving strategy I used) on my gas receipts and save them.
You can also replace your vehicle or get a second vehicle for your commute, if the math works out right. You'll need to figure out your total current and future costs for your current vehicle (not just gas), and the same costs for the new vehicle (or both combined if you plan on keeping the old one).
Basic strategies: Getting started increasing your MPG -- There are some easy changes that you can make to your car and your driving.
1. Proper maintenance -- fuel filter, air filter, PCV valve, fuel system cleaning, etc...all this stuff is on your maintenance schedule, and should be kept up.
2. Increase your tire pressure. On most vehicles you can safely increase it to the maximum pressure rating stamped on the tire's sidewall. If it affects your handling badly, lower the pressure until it handles properly. In most situations it will vastly improve your handling and tread life at the expense of a tiny stiffening effect on your ride. Most importantly, it significantly decreases the tires' rolling resistance, and so it increases your fuel efficiency. See
http://www.gassavers.org/showthread.php?t=7712 for a complete analyzation (and assurances from other sources) of the pros and cons of increasing your tire pressure beyond your car's recommended pressure. The common fears about increased inflation are NOT true.
3. Slow down. You already knew this so I won't bother explaining.
4. Don't idle unnecessarily. Long traffic lights, waiting at the drive-thru for over 10 seconds, idling in the driveway before you drive off, etc...all a waste of fuel that's currently $4/gallon. Be sure you're prepared to drive away before you start the engine -- radio tuned to your favorite station, sunglasses on, seatbelt buckled, etc. When you park, shut off the engine ASAP, even before you put the transmission in Park or set the parking brake. Your foot on the brake pedal is still holding the vehicle.
5. Drive as if you have no brakes and no accelerator. Look far ahead, plan ahead, and try to avoid accelerating or braking. When you brake, you're throwing away energy that you already paid for with fuel. See a red light ahead or a stop sign with a few cars waiting? Why are you still on that gas pedal? What's it going to accomplish?
5a. Try to take advantage of synchronized traffic lights. Accelerate briskly and drive around the speed limit and you may just sail through a bunch of green lights in a row. For routes you travel regularly (like your commute) learn the pattern and figure out the correct speed to get all green lights.
5b. Go ahead and take those corners like Mario Andretti. Instead of braking before the curve and accelerating after, you can save gas and just fly through (and therefore accelerate much less after).
5c. Keep a long following distance. Following too closely requires you to constantly adjust your speed.
5d. When approaching a stop sign with a line of cars, go slowly so you will arrive at the stop sign just as the last car is leaving. That way you avoid having to stop and go repeatedly.
6. When the weather is warm and you want to be cool, here's how you choose between opening your windows and using air conditioning:
- In stop-and-go or low speed driving, use open windows. They do not sap power from your engine.
- In continuous high-speed driving (mainly on the highway), use air conditioning, since open windows cause lots of aerodynamic drag.
Also, if you put in shades or otherwise block your windows when parked on a hot day, it will help keep the car cool so you won't need as much cooling when you drive away.
7. Automatic transmission drivers: Use Neutral when stopped at red lights (or otherwise idling but not moving). The engine keeps pushing against the brakes (with the energy being absorbed by the torque converter) while stopped. If your transmission takes long to engage D from N, try to pay attention to when you'll get the green light.
8. Use Neutral when coasting, braking, or slowing. This may be illegal in some places (due to outdated laws about control of the vehicle when technology wasn't appropriate for doing this). Depending on your specific model, coasting in gear may use more fuel than idle when, or it may entirely cut off fuel; but either way it slows you down, discarding paid-for energy just like braking.
8a. If you know your vehicle's DFCO (Deceleration Fuel Cut Off) behavior, you might want to use lower gears when slowing or approaching stops.
8b. For everyone else, use neutral when slowing or approaching stops such as traffic lights or stopped traffic.
9. Shift lower, step on the gas pedal harder. If you have a manual transmission or an automatic that makes it easy to control what gear you're in (paddle shifters, tiptronic, +/- buttons, etc), you can do this. If you have an automatic that doesn't make this easy then you can't. You may have to experiment to find the sweet spot for this; in my 2008 Volkswagen Rabbit, the best is to push the pedal to the metal and shift at 1,300 or 1,500 RPM to keep my acceleration down to a reasonable rate; but other vehicles (specifically, underpowered ones with very small engines) may be more efficient if you shift at 1,800 or 2,000 or even 2,500 RPM. If you have an automatic transmission, don't be as extreme as I am in my VW, as it could thrash the transmission fluid, requiring you to change the fluid more often.
10. Drive off-center. If you drive in exactly the same lane position as everyone else does, you're probably driving on a worn groove in the pavement. If you manage to get out of that groove, you may be on smoother pavement.
11. Limit accessory usage. Electricity for headlights or that huge thumping bass million-decibel stereo doesn't come for free; your engine has to generate that electricity. When it's not dark enough that you must illuminate the road so you can see, just use your amber lights (often called "parking lights) to make yourself more visible to others.
12. Use the correct octane rating of gas for your vehicle. If your vehicle recommends 87, use 87. "Premium" is a misnomer, implying that fuel of a higher octane rating is better. If your vehicle isn't designed to take advantage of higher octane fuel, then putting it in won't help at all; all it does is cost you more. All gasoline is required to use a decent amount of detergents and additives, so more expensive gas isn't going to help. Use exactly the rating required by your car, or if it's not available, use the next higher available rating. In older vehicles, using gas rated too low could cause damage; most modern vehicles won't be damaged, but won't be as efficient.
13. Remove unused roof racks, especially their crossbars.
14. Remove your radio antenna, or relocate it under the hood. Many people won't notice the difference in FM reception without the antenna, and if you use an FM transmitter to listen to your mp3 player you'll probably find that it works much better with the car's FM antenna removed. AM reception is usually unaffected, as the AM antenna is usually located inside the radio itself.
15. Use a MPG or fuel rate display. If your car has one, you can view the instant MPG reading to compare different ways to do the same thing (for example, which gear to use up a hill), and the trip/average MPG to determine which way is a better route. If not, there are various products you can buy, such as a ScanGauge II (currently about $160, offers lots of other functions, requires a 1996 or newer car).
16. In Stop-And-Go traffic, don't do what everybody else is doing. "Gas, brake, honk. Brake, honk, gas. Gas, gas, honk. Gas, brake honk." Instead, idle along with a big space in front of you at a steady speed. Others will jump in front of you, and most will jump right back out when the next lane moves ahead. In the meantime, you're smoothing the traffic accordion, and the traffic jam will end sooner because of you -- and you laugh all the way to the bank, saving your own gas. See
http://www.eskimo.com/~billb/amateur.../traffic1.html
Advanced strategies:
17. Drafting: At highway speeds, find an appropriate tractor-trailer to follow. Do NOT get too close! Tailgating REDUCES fuel economy instead of increasing it. Drafting behind a standard 53-foot trailer means a 2 to 3 second following distance, which is the length recommended in high school "Drivers Ed" courses, and is long enough that the truck driver can see you in his mirror. See also
http://www.gassavers.org/showthread.php?t=7219. Based on bicycling theory and experience, and auto racing data, I can say that drafting helps the front vehicle as well as the drafting vehicle.
18. Study fuel usage of your car. Use a fuel rate meter, which is tapped to a fuel injector wire and shows actual fuel rate information. It will show you information that a MPG meter cannot, such as the difference between idling in "D" and "N", and when your engine goes into DFCO mode. There are various DIY projects documented on the internet. The easiest one, which I've done, uses a $33 diagnostic meter:
http://www.gassavers.org/showthread.php?t=7714
19. Pulse & Glide: This means you accelerate briskly to a speed faster than you want to go, then coast in neutral until you're going slower than you want, then repeat the cycle all over again. It works best for me by pulsing uphill and gliding downhill, which helps keep my speed steady. There's a few reasons why this works better than a steady speed:
- Reduced pumping losses. The engine has to waste a bunch of energy to pull in air past a mostly-closed throttle that you'd use while cruising. When you pulse, you open the throttle more.
- Common engines are naturally more efficient at full load than at partial loads. Google for BSFC and look up a BSFC chart for your engine if you want. (See also
http://www.autospeed.com/cms/A_110216/article.html ). Consider that in most vehicles, the same model with a smaller, less powerful engine gets better gas mileage; this is partly because that engine may have less frictional loss, but mainly because it's running closer to 100% of its power production ability.
- Much of the time when you're cruising, you're not applying power, but just using enough gas to prevent the engine from slowing the vehicle. You're spending gas to make the engine run at higher RPM than idle, which requires enough energy to pay for the additional friction required at the higher RPM as well as all the air that has to be pumped in and out of the engine. This also explains how strategy #5 above (Use Neutral when coasting) works.
20. Engine-off coasting: This is probably quite illegal in many places, and more importantly, it's quite dangerous if not done right or if done in the wrong place/time. It will not be covered in this guide. Done safely and properly it can provide great results, especially combined with Pulse & Glide.
21. Warm-air intake, grill blocking, aerodynamic modifications, custom-tuning engines, etc: I won't cover those in detail here. Discussions of such things are easy to find on internet forums like gassavers.org. See
http://www.gassavers.org/showthread.php?t=1088 for a list of what has been tested and actually helped in the real world vs. what does NOT work.
Additional basic information:
http://ecomodder.com/forum/EM-hyperm...ecodriving.php
http://www.gassavers.org/showthread.php?t=2584
General introduction to hypermiling (canned post)
General introduction to hypermiling (canned post)
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