hypermiling works! i now get 37.5 mpg (epa says i should get 21 city / 27 hwy / 23 combined)

[unblock]

according to the epa, my 2001 nissan sentra should get me the following miles per gallon:

http://www.fueleconomy.gov/Feg/noframes/16675.shtml

MPG (city) 21
MPG (highway) 27
MPG (combined) 23


so i decided to try some of the hypermiling techniques that have been in the news recently. you know, little tricks you can do to save gas. i checked my tires, they were already properly inflated. i also didn't have much useless junk in the car. i can't conveniently carpool and i'm stuck using the car for commuting.

all i changed was my driving.

- slow down! never drive over 60mph. apparently it costs 1 mpg for each extra 4 mph of speed. hardly worth it!

- speed up! the car is most efficient in a range like 42-57mph, depending on you car. i don't know exactly for mine, but tooling around local roads at 45 mph is better than 35mph, traffic and speed limits permitting.

- smooth out the ride. the idea is to avoid hitting the gas if it later means hitting the brakes. if i see traffic or stop light ahead, i coast or tap the brakes slightly so that i "merge" with the upcoming traffic -- i meet them as i'm slowing down to the speed they're coming up to when they start to move again.

- use a higher gear. basically, i used the highest gear i could without causing the car to chug. generally if the tachometer showed over 2000 revs i shifted up.

- coast as much as possible. i have some stretches of hilly local road on my commute where i can just put it in neutral and coast for several minutes. it's actually surprising how long you can go and stay within reasonable speeds. i've actually tried turning the engine off while coasting (and back into the pre-ignition position so as to turn on power steering, etc.) but consider this too dangerous and inconvenient to be worth it. it's actually not as scary as you might think, but still not worth it.

- drive a straight line. this one probably saves a trivial amount of fuel, but it's fun. i try to straighten out my line as i drive, so i'm on the left side of the lane for a curve to the left, then gradually drift over to the right side for a curve to the right. this won't actually show up as a savings at all in mpg because you're shortening the miles driven, but in any event it's probably trivial. but it is fun :)

i'm sure i could do better, this is only the first tank of get i've tried this on. from fill-up to fill-up was 405 miles with 10.787 gallons = 37.545 mpg. i used the exact same pump both fill-ups so even the shut-off would be the same.



as all articles on hypermiling note, some of the techniques are not very safe and some are even illegal (rolling through stop signs, e.g.) but can be used within reason.

of course, YOU MILEAGE MAY VARY, but then again, that's the whole point!

[LisaM]

1. What about drafting when you are next to big trucks?

That can be fun!

[Tikki]

6. Oh my...please think before...

you draft behind a semi-truck. If you are back there
riding his rig it means he has to pay constant
attention to you back there.

I bet most rig drivers would ask you not to draft behind them.

Tikki

[LisaM]

11. I don't STAY there!

If I do this, I just do it for a few seconds. Don't worry (I am a safe driver). If I do this, it's usually in the nature of easing up just a little as I'm passing them.

[Tikki]

14. OK....

:)


Tikki

[A HERETIC I AM]

16. There is ZERO aerodynamic advantage to driving along side a big truck.

If you could see the way the air is tumbling and churning alongside a truck as it goes down the road, you would understand why.

The flat rear end of a truck creates a low pressure area that extends for some distance behind it and that is why mileage increases when drafting. There is no such low pressure area along the side of a moving truck.

[unblock]

18. actually, there is, but it sucks you in toward the truck!

it doesn't help you move forward. it would help you move laterally if you really wanted to "slingshot" back and around a truck. not sure why you would want to do that unless you were racing....

[unblock]

8. one can only take so much fun :)

:scared:

[A HERETIC I AM]

10. Please DON'T!

It's not worth the risk.

I drove heavy trucks for twenty years and one thing that used to totally piss me off was someone too close to my rear bumper. Many trucks now have a sign that says "If you can't see my mirrors, I can't see you."

More accurately they should read "If you can't see me in my mirrors, I can't see you".

While it is absolutely true that driving in the slipstream of a large truck can dramatically improve mileage (Mythbusters did a segment on this) the fact is, if a large truck has to brake suddenly, the closer you are, the less time you have to react. Also, running too close to the back of a truck can hide road hazards like debris in the road. A big truck can easily straddle something that will severely damage your car, should you run over it (a hunk of 4X4 or a tire tread, for instance).

One thing I've noticed about this Hypermiling concept that is flawed is what is happening to those behind you. Delaying or slowing cars behind you because you are accelerating slowly away from a stop light helps you and ONLY you. The others that missed a light because you didn't get on with it are now stuck at the light, wasting even more fuel.

Keep your tires properly inflated, drive with the flow of traffic, accelerate smoothly but not too slowly and minimize trips will save plenty of fuel. Holding up others will not.

[NNN0LHI]

19. Anyone who would tailgate a semi-truck is someone who has never ...

... seen a truck lose pressure to its air-brakes while tooling down the highway at 60 MPH.

I have seen this occur recently to a truck heading toward me on a two lane highway. Lot of action. And smoke. He jackknifed and had both lanes completely blocked before it was all over.

Don

[LisaM]

20. All right! All right!

But I don't tailgate and I don't drive right behind the trucks. I just use a little of their draft when I'm passing by easing up on the gas at the end. I don't tailgate period. I always (or to the extent that I can) count a full two seconds between the vehicle in front of me and my car - by choosing a fixed object and then counting the seconds - which works at any speed. I think tailgating is the most dangerous thing you can do.

[flvegan]

2. Pre-ignition won't give you power steering nor power brakes.

Turning the car off to coast is a bad, bad idea.

[unblock]

7. i guess i didn't try it long enough to really notice a difference

power steering and power brakes are ... well, we're talking about a nissan sentra here, so who needs it anyway?

i have turned the car off when stopped at a long light. unless i'm at the front of the queue, i always have enough time to turn it back on again, especially if i can anticipate the green based on the flow of traffic through the intersection.

[A HERETIC I AM]

12. Agreed.

Power steering relies on an engine driven hydraulic pump. Turn off the engine = no pump.

Power brakes rely on the engine also. The brakes will still work, but they will not work nearly as well as they do with the engine running.

[unblock]

15. i think you get some assist from a *recently* turned off engine

i think i read somewhere that the pump is useful for a short while before the fluid completely flows out?

anyway, i think the "engine off while coasting" technique is clearly only safe for hybrids where "engine off" merely means "running on batteries".

[A HERETIC I AM]

17. Sure. While there is still pressurized hydraulic fluid, it will help the steering...

but that advantage will soon go away.

I agree with you re: Hybrids. They are designed to run that way with no ill effects. The average, non-Hybrid car is not.

[sandnsea]

3. Never heard the higher gear one

I have a tendency to stay in the lower gear so I will definitely use that tip. I can't go over 40 in my town, so the speed tip isn't any good. This also reminds me to check my tires. Every little bit helps! :hi:

[pimpbot]

4. Depending on your gearing you can go faster than 60MPH

I can't even get into 6th gear going 60, because its too slow and have no torque for hills etc. At 74MPH I'm right around 2000RPM and have enough oooomph to accelerate for hills etc. I also coast alot and try to time lights in the city. If I see the light ahead just turned red, no need to race up to it.

[onehandle]

5. I floor my Hummer with the emergency brake on wherever I go.

USA! USA! USA!

[elocs]

9. From USA Today: Police monitoring hypermilers.

http://www.usatoday.com/news/nation/2008-07-07-Hypermilers_N.htm?csp=34

BOISE (AP) — Motorists who try to increase their gas mileage by coasting with their engines off, drafting behind big rigs and driving much slower than the speed limit may be acting dangerously and even illegally, officials say.

"Hypermilers," as they're known, say those techniques and others, such as overinflating tires, can help them get 80 to 100 miles a gallon in a normal car, saving on gasoline that costs more than $4 a gallon.

"The goals of hypermiling are positive, such as eliminating aggressive driving and saving energy," Marshall L. Doney, AAA Automotive vice president, told the Idaho Statesman. "Unfortunately, some motorists have taken their desire to improve fuel economy to extremes with techniques that put themselves, as well as their fellow motorists, in danger."

Adam Winstral of Boise uses some of the techniques but doesn't consider himself a hypermiler.

"Coasting to red lights, turning the engine off at long red lights," he said. "It's simple, and you don't have to piss others off.

My guess is that for some pissing off others is either half the point or half the fun. Apparently lots of cops and state patrol do not look favorably on some of the aspect of hypermiling that its enthusiasts like to embrace.

[unblock]

13. agreed, you have to use your judgement

you could obviously save get by coasting right through intersections, ignoring signs and signals altogether!
but saving gas isn't the only goal. one accident or ticket easily wipes out all the savings!

as for speed, i find simply sticking to the actual speed limit (not the typical 8-10+mph over) often works quite well.


you're also not being a good carbon citizen if your slow driving causes others to slam on the brakes behind you and then floor it to get around you. in fact you might even be INCREASING your overall carbon footprint by doing that!

most of the techniques work best when there's no traffic or at least when traffic is predictable.

[tech3149]

24. Some of the techniques used by hypermilers are stupid and unsafe

They might achieve their goal but can the cost be justified? I might not have much to live for but I understand that my stupid choices might hurt someone with people who rely on them. I can't bear that burden and won't take that chance.

I don't have anything against the LEO's, they're just doing the job they were paid to do. I've been qualified as a "persistent violator" because I tended to drive well beyond the speed limit. My current view of performance driving is to spend as little as possible to do what I must. I cruise stop signs and don't observe lane markings if they get in the way of my efficient travel. BUT! I don't take my life or anyone else's as having no value. I've got no problem dealing with the pedestrian drivers except for containing my rage. Through my entire adult life I've seen the driving skills deteriorate and I won't even try to guess why.

I think we should all keep our heads up and turn up th BS detector.

[Fumesucker]

21. A few points..

Fairly brisk acceleration is more fuel efficient than very slow acceleration as long as you keep the engine rpms down (early shifting). Otto cycle engines are generally more efficient at a high percentage of maximum torque as long as you are still running closed loop. This is easy to accomplish with a manual transmission and rather difficult with an automatic. On my automatic truck I press the throttle until 2000 rpm or so and then back up to let it shift and then press again.

Drafting semi trucks increases fuel economy back to somewhat more than one truck length behind the truck, you don't have to ride their bumper to get an increase in mpgs.

Pump up your tires to the maximum pressure listed on the sidewall, for a lot of modern tires this is 44 psi. The sticker pressures on the car are generally the *lowest* safe inflation and increasing pressure over that will both increase fuel economy and improve general handling of the car, plus it will most likely make your tires last longer.

I can hypermile and very few of the people driving around me will even notice, you don't have to drive like a Florida blue hair to significantly increase fuel mileage. For example, my 97 Expedition tow vehicle with a SOHC 5.4 is rated at 12 mpg city and 16 hwy, I average 17 and 22 mpg respectively. I almost always do at least the speed limit when not towing and when I am towing, people expect somewhat slower driving so it's not a problem.

Turning the engine off at long lights or other stops can significantly increase your overall fuel economy, I'm really surprised by how much gas my truck uses when idling and how much it hurts my overall economy. It was very hot the other day and I made a 66 mile run with a 3800 lb load (total vehicle weight over 9600 lbs) on my medium flatbed trailer with the AC on, got 18.5 mpg while I was driving but I left the vehicle idling for about 20 minutes while I unloaded because my grandson was in the truck.. My overall mileage dropped to 16.7 over 66 miles due to the idling.. And I didn't have the AC set on quick chill, it was just enough to keep the interior reasonably comfortable, the second setting out of four.

I've developed these tricks over the last couple of years of driving a heavy tow vehicle with an onboard MPG gauge for my business, wasting fuel takes away from my bottom line so I have carefully monitored my efficiency, both with the onboard gauge and with the traditional odometer/gas pump readings.

[tech3149]

22. Congrats and welcome to the club!

Another couple of tricks to use that also increase safety. Keep a solid 4-5 vehicle lengths between you and the car in front of you. You'll have a better field of view and can anticipate what you might have to do sooner. Mileage wise, it will keep that vehicle from controlling your speed. Slowing down and re-accelerating wastes a lot of energy.

Maximize your situational awareness. One of the things they teach in racing school is to focus your attention on the farthest point of the roadway to anticipate situations you might have to correct for. You can develop your peripheral perception to keep track of those things happening right in front of or around you. On the street, this gives you the chance to avoid wasting energy by slamming on the brakes only to return to normal speed. If you see someone ahead of you trying to make a left through oncoming traffic, back off and brake early. This might save you from dropping down to 1st or 2nd gear before you get back to normal speed.

Momentum is your friend and gravity is free energy. It may not be the most comfortable ride for your more delicate passengers, but maintain your speed through the turns, even the cheapest retread can handle the lateral load that would be comfortable to the average driver. To ease the load and avoid wasting energy, enter the turn as far to the outside as possible and turn gently to the inside shoulder at the middle of the turn. Unwind the steering to exit the turn as far to the outside as possible. The bigger the radius of the turn is the less speed you lose from friction. On sections of the road where you have unobstructed view, don't be shy about using both lanes (unless it is a likely that local law enforcement might be looking over your shoulder). Never underestimate how much energy it takes to get through that turn.

Gravity, fight it or use it. You can't change the terrain but you can make the most of it. If you have to accelerate on an uphill section, don't be impatient and go slow and steady. As you approach the crest of the hill, back off the throttle or upshift. If you are starting out on a downhill section, skip a gear or for automatic drivers play with the throttle to get it to upshift early. When you know the terrain you can use it to your advantage. It takes less energy to accelerate downhill or on the level than it does uphill. If you get a feel for your engines power curve you can figure out where you need to start accelerating to clear the hill without downshifting.

Many of your observations show that you have an understanding of the physics involved. I hope my comments help to educate some of those here that are really being hurt by the cost of fuel.

BTW My ride is a 98 Honda Civic, manual everything with 32/37mpg figures. I can do 40 mpg around town but not much better on highway trips because I get itchy on my right foot when people pass me.

[scheming daemons]

23. Fine... but if you're going to stay under 60..... STAY OUT OF THE LEFT LANE

You create a dangerous situation if you drive that slow in the passing lane on the highway.

[unblock]

25. don't worry :)

safety comes first and the road must be shared.
driving at the speed limit, one rarely passes, hence one has little use for the passing lane!

[FourScore]

26. Be careful coasting.

I've heard it can be dangerous on slick, wet roads or hitting oil spots. It can lead to hydroplaning. I do't know if it's true, but that's what I was told.

Thanks for the info. All good to know.