Economy

[waif69]

Recently I read about how hypermilers are getting amazing fuel economy out of their cars. So I decided to try some of the tecniques.

Before I started I was getting about 30.5mpg commuting. By turning off the engine when slowing to a stop or going down some big hills (of course minding the amount of cars on the road, this isn't always possible), I have been able to get my economy up to 36mpg. I know this isn't a huge difference, but it is a start. I also drop the clutch and let the already spinning transmission start up the car.

Have any of you tried this? What are you performance results?

[noisewatter]

I do it; I live in an area with a lot of hills that is very rural, and I can coast at about forty five miles per hour for a good mile of so. My economy during my regular commute is about forty three miles per gallon or so, depending on traffic; I use about a quarter tank per week.

[steelmalu43]

I heard about those hypermilers when i was up in NY in May, so i decided to try some of those techniques on the drive back to SC. On the drive up i got 27 mpg and on the way home using some of those techniques i got 30-31 mpgs. This was with my monte carlo (since i dont have the xd anymore). I know i'll never get as good of mileage as i did with the xd but i'm getting an average of 28 mpg's with the new monte so its not that bad considering i jump up 1.5 liters in engine size.

[Cypher]

I just filled up today to receive 36.7 mpg

[cobase]

I tried "light," hypermilling, i.e. I left a huge following distance to avoid using the brakes, looked for red lights as far as visibility would allow, turned the engine off at long red lights where I know the cycle and kept accelration to low RPMs. My fuel economy improved from about 22-23mpg to 28.6mpg for a week. However, driving that slowly and getting cut off so often just didn't make it worth it for me.

I briefly tried coasting with the engine off down long hills and I think it makes a big improvement over idling, BUT I think it's just too dangerous. Power steering is gone, the brakes only work once or twice, and you'd better not turn the key to "Lock," if you want to steer. Plus you're worried about when/how to start the engine again and the rest of the demands of driving in traffic... no thanks.

The last week, it's been so muggy around here, the A/C is killing my economy. I'm down to 23 again. :(

[shapu]

Hints for fuel economy:
1) The best bolt-on addition is the one already bolted to your right ankle (it's your foot, in case you were wondering). Lay off the freakin' jackrabbit stops if you want to save gas.
2) Don't use your breaks on the highway. Use of breaks is the same as admitting "I used too much gas 10 seconds ago." This means don't drive like you have to use them, either.
3) Coasting = good.
4) Drive-throughs = bad.
5) Change your oil and use the right oil for the weather. Make sure your mechanic actually changes your oil filter if you don't do it yourself (yes, this happened to me twice at two different places).
6) Don't use A/C below 45 mph. Because it's connected to the serpentine, using the A/C uses power generated by the engine. However, above 45 miles per hour, having windows down creates turbulence around the car that affects gas mileage.
7) Don't be afraid to drive when it's warm outside. *Informed opinion with no data to back it up or refute it as far as I know follows*: Warm air actually improves gas mileage because it increases the amount of heat in the combustion chamber (each chamber is a closed system during the combustion cycle). Increasing total heat increases the odds that any individual fuel molecule will reach the activation energy necessary to combust.
8) Don't drive with a trunk full of pipe wrenches unless you're a plumber and also Doctor Octopus.

[Tommy]

36mpg is pretty close to the top end of mileage on these cars without getting crazy. Im able to average 38 or so on the highway without much effort. Easy starts, driving ahead of where you are, ie, keep in mind where youll be in the next 20-30 seconds, and keeping it below 65, if not 60 on the highway and 38 is pretty easy.

Best ive done was 43mpg over 400 miles. Ive taken a hit since then due to some heavier wheels. Since the wheels, best i can do is 40.

[Matrixloader]

best i have gotten was 40.1 mpg on a long trip.

[steev-o]

I just filled up today to receive 36.7 mpg


that is soooo freaking awesome dude. What have you done to your engine to have it run so perfectly. did u pull out a cylinder? mounted pedals in the footbay?

please let me know what your current setup is... so i can try to achieve this as well.

I''ve been putting the car in neutral like 200 yards before a stoplight and leaving it in neutral till the green light comes on. I think its been making a noticeable difference.. since im at 260miles now and still have 1/4 th of my tank left.

[04GTboySC]

im goin on a road trip to NY end of august so im gona be all about seeing how my gas mileage is, around here in charleston im only able to get 24 mpg and like steev-o i have been putting it in neutral at stop lights not sure if its helping since i dont see a big improvement

[2003GT]

I have put it in Neutral going down hills and such but I dont want to screw up my tranny. Shutting your engine off is just taxing your batters and your starter. There is no need. i f you want better mileage get a hybrid.

[bdiggy]

I'd have to say i'm with Cobase on the dangers of shutting down the engine and coasting. Loss of brakes and steering would most certainly be a bad thing. I'm only getting a little better then 29 mpg right now, but it's a lot of stop and go.

[waif69]

So far I am getting 35.9mpg, according to the computer, but that is me getting a little crazy. I don't know how long I will be able to keep up with the behavior changes.

[04GTboySC]

lol behavior changes good one but ya i know what you mean
its better to drive the actual speed than to drive really hard
i would never shut the car off but i do coast down hills if able to

[kylemorg]

^ definitely. If you accelerate slowly, coast when you can, and keep your top speed lower you'll get better fuel economy. I got 38.5 mpg coming back from New Columbia PA to Pittsburgh, about 245 miles driving at ~50 mph on three heavy rims and a donut spare last fall. It was painful time-wise, but I was amazed at the fuel economy!

You will reach a point with behavior and minor modifications (tire pressure, etc.) where the limitation is the efficiency of the engine and powertrain (and the hills / stops-starts on your route). That will be the point for maximum fuel efficiency -- your car has to generate enough power to push your car from point A to point B and requires X gallons of gas to do it.

[Silentwolf]

A taller 5th gear would be the best modification for our cars!

[shapu]

Question: Does sliding the car into neutral while moving damage the transmission? I have never heard that before, and I'm sure it is in fact rather incorrect (although it is apparently illegal in many states).

Additional point: Keep your tires inflated, and if possible, use nitrogen rather than pressurized air (available at CostCo). Nitrogen molecules are larger than oxygen molecules or helium molecules, which means that H2 and O2 can dissapate through the gaps in the rubber of the tire more easily than N2 can - this reduces tire pressure and makes your car less efficient. Having N2 in your tires (which is also less susceptible to heat expansion) is a good idea if you can do it.

[kylemorg]

Smoothly shifting in and out of neutral should be fine (on both manual and automatic transmission cars) while moving. I'd recommend against turning your engine off while the car is in motion since you lose vacuum generation (and eventually power assist on the brakes once air bleeds into the vac assist line) and your power steering.

Nitrogen expands the same as air (~78.1% nitrogen ~20.9% oxygen, 0.9% argon and 0.1% other gasses) across the temperature range that car tires see (-20°F to 212°F). Other than the permeation rate and oxidation of the tire itself, there's no real difference between the two for on-road automotive use. I calcluated the expansion of a nitrogen atmosphere and a nitrogen / oxygen mixture based on the actual expansion coefficients for each gas based on the handbook of chemistry and physics I have on my desk at work. in a post here but it was lost during one of the crashes about 6 months ago.

Also, since oxygen permeates through the tire wall faster than nitrogen, if you keep topping off your air pressure (lets say you let it drop to 30 psi due to permeation and take it back up to around 36 psi) six times or so, the relatve % oxygen drops to around 2% since the nitrogen remains in the tire longer. You'd actually be better off filling your tires with Argon (inert and larger molecule) if it was readily available.

Just check your tire pressure every couple of weeks and keep it where it should be.

If they were airplane tires or racing tires exposed to higher temperatures and more extreme and longer (years of) use, then nitrogen might be worthwhile.

[2003GT]

So I guess I was wrong but I have always heard Neutral drops was bad especially while its running. I did it and when I slid it into drive the car like acted funny it jolted a little. Also In one of those Hypermilling articles it said idling wastes gas. With the car in neutral essentially you are just sitting there idling the car while its moving.

[NovaResource]

Coasting in neutral is actually less efficient than coasting in gear. Here's why: most modern engine shut off the fuel while coasting.

When the car is in neutral the injectors are pumping fuel to keep the engine running. Just like idling while at a stop. At least you are moving but the engine is still using fuel. However, when coasting in gear, the engine is not using fuel because the inertia of the car is spinning the engine via the wheels and transmission. Because of that, no fuel is needed to run the engine. The only downside is that the engine is placing drag on the rear wheels, slowing the car faster than it would if coasting in neutral. This is why hypermileres shut off the engine. No fuel to keep the engine running and no drag because the trans is in neutral. However, this is unsafe as mentioned above.

I follow some hypermiling techniques:
- coasting (in gear, engine on)
- high use of cruise control
- slowing down
- slightly higher tire pressures (emphasis on slightly)
- maintaining distance from cars in front to allow coasting to a stop and avoid using the brakes
- light acceleration

I will not shut off the engine while moving, tailgate tractor-trailers or take turn at too quick a speed just to maintain momentum. All are unsafe.

[bmxdad]

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Its Delta V6 is a torqueless, inefficient, gas-guzzling, underpowered engine.
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[RotaMan99]

6) Don't use A/C below 45 mph. Because it's connected to the serpentine, using the A/C uses power generated by the engine. However, above 45 miles per hour, having windows down creates turbulence around the car that affects gas mileage.


Its not going to hurt your milage that bad at all. I my self will use the A/c at stops all day long. Driving above 45mpg with the a/c on, the a/c still takes the same amount of power to run it.... so it makes no difference.

When your coasting down a hill, you are using almost zero fuel. Very very little is being injected and I mean, A:F gauges can not register the A:F ratio correctly its so lean.

Turning your engine off while coasting isnt going to be much of a difference. My MPG goes up like hell on deceleration.

[Cypher]

it depends on your RPMs as far as how lean you are on deceleration. Once you get down to like 2-2.5k rpms with your foot off the pedal then the fuel kicks back in and start running around stoich. Above that my wideband pegs at 22:1

I also don't do anything special. I drive exactly as I always have.