questionshypermiling: do you do it? have you heard of it?

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I don't, given I take the subway to work. But here are a few additional tips I've picked up over the years that help MPG:

- Keep your tires at the proper pressure (easily found in your owners manual). High or low pressure can negatively affect mileage quite a bit.
- Don't drive with your windows down. Creates a lot of drag. If you're hot, A/C is actually more efficient than windows down.

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I drive a hybrid SUV and do everything I can to keep it on battery, not using gas. Over almost 15,000 miles my average is 33.8 MPG. Best tank so far was over 40 MPG.

I do the normal stuff - being careful on the go pedal, coasting to stop signs and traffic lights whenever possible, keeping the tires slightly overinflated. I've also measured various grades of fuel and found no advantage to mid-grade. Some cars react well to accelerate-coast operation (hit the gas to speed up just above your target speed then get off the gas until you slow down below it, repeat.) You'll have to try that to see how it helps.

Given all that, the range from the worst tank for me (23 MPG) to the best (40) is 17 MPG. That really bad tank was due to driving in a snowstorm causing total gridlock: over two hours to drive about 8 miles. That caused the car to eat gas.

I'd be surprised if you really get more than 5-6 MPG improvement due to driving behavior unless you're comparing to a really poor baseline.

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I have a hybrid car and braking is actually good for the MPG. It recharges the battery by using the motor as a generator. This is why I get better MPG in the city than I do on the highway.

I tried to follow semi-trucks closely and that does reduce drag but I don't feel comfortable following that close for safety reasons.

Regarding the A/C, I leave it where it's most comfortable knowing that will affect my MPG but I don't care. I like to be comfortable even if it costs me a little more.

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No I don't. And I hate those guys. So many of them block the roads, are in the wrong lane, take forever to get up to speed on the highway, etc.

They contribute more to road rage and their own potential demise than what they save.

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@mtm2: I think you're just referring to poor drivers. not necessarily someone trying to save gas :)

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@novastarj: Whether it's better to have the AC on or windows down depends a lot on the speed at which you are driving as well as the vehicle. The break even point for air conditioning on vs windows down is going to be different for every vehicle and, since I've only done wind tunnel testing on aircraft, I don't have any data to help in estimating what that speed would be. But I would say that a good rule of thumb would probably be around 45-50mph. Below that windows are probably more efficient. Above that air conditioning is probably more efficient.

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Ten to fifteen mpg? Really? That's...a little hard to believe. For most cars, that'd be a 30%-40% improvement in mileage. I'm not calling BS, but I'd be interested in seeing it done outside of "extreme hypermiling" competitions.

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My husband used to do that. He was able to get 32 mpg in a Toyota Tundra. I have always found it annoying and troubling to other drivers.

He doesn't do this anymore. Probably because I am always in the car with him.

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My friend drives a small manual pickup, and he keeps the engine off about half the time when he's driving. There are long, slow hills on the highway, and streets are fairly hilly, so he turns off the engine at the top and just coasts till he starts to lose momentum. He can often go several miles without falling below the speed limit. The main inhibitor is when he comes up behind some slowpoke that forces him to brake and lose momentum, then he has to start the engine and get back up to speed. He gets over 40pmg on a 10+ year old truck with over 100,000 miles on it. I depress the clutch and coast down hills in my Civic, and I always use the cruise control when on the highway. The main way I save gas and the environment is living less than 4 miles from my office, maintaining my car in peak condition, shopping close to home when possible and combining many different errands together when I have to go to a commercial part of town. I'm ok w/the the A/C set on 1 of 15 (it's 104 today).

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what bothers me is the guy you pass trying to "hypermill" when in reality he might be saving gas he is costing everyone else alot in saftey. Example @moondrake what your friend does is not very safe with his engine off he cant gun the enginr and move or adjust the way you should be able to.

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@moondrake: You should let your friend know that actually turning the key and shutting the engine off does him no good on a manual. I think any FI engine attached to a manual transmission will automatically cut off fuel the injectors when engine braking all the way down to idle speed (200-300RPM) So all your friend has to do is leave his truck in the highest gear and let off the gas pedal and he will accomplish the same thing in a much safer manner.

@everyone-else I'm using my car's EPA estimates for my baseline. My commuting car is rated at 33MPG Highway, I average 45MPG (70% highway, 30% city) in the summer months, and it declines slightly during the winter. I do believe I get the most fuel economy boost when I draft larger vehicles. I do not drive abnormally slow, the slowest I drive is how fast the truck in front of me is going. I didn't realize this question would generate so much hate!

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I don't do the extreme hypermiling techniques that some do (like pulsing), but I do drive as smoothly as I can. I must be doing something right, because my average commuting mpg typically meets or beats the EPA highway mpg for my vehicles, and that includes some stop and go sections as well as crossing a medium sized mountain (~750 ft elevation gain) each way.

What many lead-footers don't understand is that it is very difficult to have an individual average speed that significantly exceeds the average speed of traffic, regardless of bursts of increased speed when it is possible over some sections and weaving back and forth in lanes to pass. At the next stoplight or traffic slow down, everybody pretty much evens out again. Some honest experimentation driving your normal route with a stopwatch over a few days can be a real eye-opener.

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I do not hypermile.

For me, part of the driving experience is having fun. Driving slow is not fun. I do not speed excessively (I usually keep it within 8-10 mph over the posted limit), but I do like to get to my cruising speed as fast as I possibly can. I like taking corners as fast as my tires and the situation will allow.

According to the reviews, my car can go 0-60 in 7.5 seconds. I like the way that feels.
According to the reviews, my car can hold 0.92g on the skidpad. I like the way that feels.
According to the speedometer, my car will do 140. I do not know how that feels.

I am at the point in my life where I can afford some extravagances. Paying a little extra for fuel is not going to break the bank.

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@lumpthar: I agree with you there, my OTHER car does 0-60MPH in 5.5 seconds. Does .87G on the Skid Pad. And has AWD. I LOVE the way all that feels.

I just find it fun to do one or the other appropriate times. Maybe I'm semi-obsessive but getting the most fuel-economy out of my '01 Honda is fun, and keeps my entertained on my commute to work.

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Mythbusters has tested a few of these hypermiling techniques on different episodes of their show.

For AC vs windows down, it's like @gt0163c wrote: above a certain speed, AC is better as it reduces drag; under that speed windows down is more fuel efficient. For the Mythbusters, the over/under point was 50mph:
http://mythbustersresults.com/episode38

For drafting a big-rig, there isn't a way to do this safely. You do get results, but you have to be closer than the minimum recommended following distance of 150ft at 55mph. Closer than that and the truck driver may not be able to see you, and you may not be able to stop in time if the rig stops suddenly. 3/4 of truck/car accidents are caused by the car being in the big rig's blind spot.
http://kwc.org/mythbusters/2007/06/episode_80_big_rig_myths.html

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I don't. Most of my commuting is 1.5 miles to work, and 1.5 miles back.

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@eraten: Okay, I'll grant you that it is a challenging endeavour to try to go as far as you can on a tank of fuel. You have scenarios and data and maths all floating around your head.

It's a giant optimization study, only in real life and in real time.

That's just not something I have the patience for.

That being said, my car gets 31.5 mpg on the highway with a roof rack and a lead foot. I'm pretty happy with that. It's fun to drive, too.

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Yes, and for my daily commute (about 8 miles, half of which is highway driving), hypermiling boosts my normal MPG by about 25% (from ~16 to ~20) and adds about five minutes to my 15 minute commute.

Driving very aggressively (jack rabbit starts, braking much more than I usually do) drops my MPG by about 33% (from ~16 to ~11) and cuts about three minutes off of my 15 minute commute.

Driving like the people around me (ie. more aggressively than I usually do) drops my MPG by about 15% (from ~16 to ~14) and might cut a minute off of my commute.

All in all, none of this really matters as my yearly commute is less than 1800 miles and the difference between 11 MPG and 20 MPG is less than $6 a week at $4/gallon.

BTW- this is a well maintained 2004 Ford Taurus SEL. On a fairly flat highway with no major wind, it gets ~24 MPG with the cruise control set at 65.

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@baqui63: I've got a 2002 Taurus wagon. On a fairly flat road (say Texas) I used to get 27 mpg at 75 mph with the AC on. Slowing to 65 does not improve the mpg. Nor does 55.

I can only assume it is due to drag coefficient, gearing, etc.

My mpg has dropped over recent years. It's due to the car having 170K on it and showing signs of it's age (a problem I seem to have as well).

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@marsilies:

Not for the testing... it was mostly in the Fall and Winter, plus most of the commute is at 35-40 MPH or less.

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@mtm2:

Hmmm... I might be getting as much as 25.5 (I rarely drive long distances at speed, so there could be a fairly large error) but no way could I be getting 27. I don't know the differences between our cars (engine specs, for example) but unless there is a real difference, I wonder why I'm getting lower mileage, especially since I'd think that the sedan would be more aerodynamic (less drag).

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@lumpthar: I understand the enjoyment of feeling your vehicle respond in a spirited manner, I really do. But if you are OK with paying a bit extra for your entertainment and extravagance, why not take it to a real track and do it right instead of pretending on the public streets?