Hypermiling and Gas saving Tips

[MyMeowCat]

Hi There!

That thread about the Toyota Prius vs. Hummer kinda inspired me to write this and ask a couple of questions.

There is a new practice out there called hypermiling (meaning to drive in the most gas saving efficient way possible to squeeze the most out of every drop of gas).

I know most of you have heard about things like keeping your tires inflated right, getting a tune up, planning your trips/avoiding un-necessary trips etc., and basic things like coasting to a stop sign/red-light.

There are those who take it to the extreme however. I decided to experiment with it a bit this last 2 weeks using my 6 cylinder standard transmission 2002 Pontiac Pursuit.

I was just wondering if any of you would have the automotive expertise to comment on the following:

1) Instead of just coasting to a red light (especially when going down a hill) -- turn your ignition off...let inertia glide you there. Theory -- when coasting (with foot off accelerator) -- your engine still "idles" and uses up gas...so turn off the engine and use the built up inertia. If you are idling at a stop light -- you are using gas to get zero miles per gallon! Restart engine when light turns green.

If you have a leased car with an electronic odometer -- turning your ignition and power off allows you to coast significant distances that are not recorded on the odometer and thus saves you on leasing costs. It could build up over time.

If it looks like inertia won't get you to the stop sign -- push down on the clutch pedal so the friction from the engine/drive train etc. won't slow it down.

QUESTION: Isn't this hard on the starter motor and wear and tear?

2) I found a this one on Youtube.com -- Wait until you are nealy empty before refueling because if you have more fuel -- you have more weight. Other than doing price speculation on gas (in other words -- I'd fill up now rather than over a long weekend or when ever I think before gas is going to go up mentality) -- Lets take this one step further! Let's put your car into the "Utility" category.

Carry only enough fuel to get from Point A to Point B Plus an extra 45 minutes or whatever school rules are. This means your car carries less weight. If you do go to a gas station -- fill up only what need to get home in your tank and put the rest (say approx 40 liters) in a jerry can or gas container to take home...refuel using the jerry can or gas container before going on a round trip to and from work/destination.

COMMENT: I've never done this before (afraid my garage with fully loaded gas cans can be a hazard) -- but what effect do you think #2 would have??

3) Tune ups and changing air filter etc...I wonder what your cost of tune-ups are and changing oil filters/tires, ect...

Obviously it increases your gas milage but does that increase in gas milage offset the cost of the tune-up?? I remember owning a 1984 Trans-AM -- milage sucked so I got a tune up and it didn't seem to improve my milage much.

MyMeowCat

[B-rad]

Hey, tried this hypermileing for a couple months back and i found it to almost not be worth it. like you said... i was able to stretch my tank an extra bit.. maybe 40 k or so more then i normally get and that allowed me to avoid a fill up until the price went up another hike and i almost broke even. as well, it cost me the hassle of always having to be aware of my coasting and only sometimes did i turn the ignition off.. seamed to be more of a pain then the few hundred meters it saved in gas mileage. Overall, I found I can get the extra distance out of the car best by doing the speed limit driving and being easy on the gas. once you start the HYPER part of the routine... how about you recycle bottles a little more for the benisit your going to get. or turn your lights off when your not in the room. I think there are safer, easier, more efficient ways to save energy then holding the speed around a corner while in neutral to save 1000 rpm for 10 seconds.

my 2 cents.
would like to hear others stories.

[xsbank]

Fuel is still the smallest component of operating/owning a vehicle. Wait 'til you add the cost of a cauliflower at Christmas, well into the heating season, then you'll really be able to appreciate where your money went.

One of these days you'll be coasting along without yer steering and brakes and you'll hit something and we'll be able to add yer name to the Darwin Award recipients, especially if you have a can of gas in the trunk to provide some background lighting.

[KAG]

If you want to save gas, drive slower, resist the urge to hammer the gas pedel. If you really want to save gas buy a diesel. Yes diesel is more expensive (7 cents/litre more expensive) but then again I get around 1000K per 55 liters on my 5spd, and 850K on my auto. a gain of about 300-400 K over most cars.

[co-joe]

I hope you guys doing this at least do so in the slow lane. Some of us have somewhere to go and don't have all day to get there.

[hazatude]

Just by driving slower and not accellerating hard, I got and extra 70kms on my last fill-up.

[Starsky]

1) Instead of just coasting to a red light (especially when going down a hill) -- turn your ignition off...let inertia glide you there. Theory -- when coasting (with foot off accelerator) -- your engine still "idles" and uses up gas...so turn off the engine and use the built up inertia. If you are idling at a stop light -- you are using gas to get zero miles per gallon! Restart engine when light turns green.

If you have a leased car with an electronic odometer -- turning your ignition and power off allows you to coast significant distances that are not recorded on the odometer and thus saves you on leasing costs. It could build up over time.

If it looks like inertia won't get you to the stop sign -- push down on the clutch pedal so the friction from the engine/drive train etc. won't slow it down.

QUESTION: Isn't this hard on the starter motor and wear and tear?

This one is wrong. A modern fuel injected car with a standard transmission will not inject any fuel into the engine when you lift off the gas while coasting in gear. The drivetrain continues to turn the engine over, but there is no fuel going in. If you were to shift to neutral then it would start fuel flow again so that the engine will idle.

Also, by shutting the engine off, you will loose the power brakes (vacuum assist) and the power steering if you are costing in neutral. Have fun stopping or avoiding the kid on the bike that just crossed the road in front of you without looking because he didn't hear you coming....

2) I found a this one on Youtube.com -- Wait until you are nealy empty before refueling because if you have more fuel -- you have more weight. Other than doing price speculation on gas (in other words -- I'd fill up now rather than over a long weekend or when ever I think before gas is going to go up mentality) -- Lets take this one step further! Let's put your car into the "Utility" category.

Carry only enough fuel to get from Point A to Point B Plus an extra 45 minutes or whatever school rules are. This means your car carries less weight. If you do go to a gas station -- fill up only what need to get home in your tank and put the rest (say approx 40 liters) in a jerry can or gas container to take home...refuel using the jerry can or gas container before going on a round trip to and from work/destination.

COMMENT: I've never done this before (afraid my garage with fully loaded gas cans can be a hazard) -- but what effect do you think #2 would have??

This one makes sense on first glance until you do the math on it. Your average Japanese small car has about a 45 litre gas tank. Since gasoline weighs something like 1.6 pounds per litre, with a full tank there is less than 75 pounds of fuel in the car. Now, if you are like me then you fill the tank when it is almost empty. This means that on average there is about half a tank of fuel in the car or about 35 pounds. Now look at the proposed scenario, only carrying enough fuel to get where you are going means that you will have say a quarter tank when you put gas in, so 15 pounds. This means that on average you have about half that or 8 pounds of fuel in the car. All of a sudden we are talking about the fuel used to carry around an extra 27 pounds of fuel. I think that I'll go on a diet and lose 27 pounds so that I don't have to stop for gas every single time that I use the car. Never mind the hassle of running out of gas because you are always trying to push it to the next gas station....

[x-wind]

If its an automatic thats hard on the tranny because its not being lubricated properly. Also careful power no power assisted brakes could be a surprise..

Drive slower yes. Use brakes as little as possible - higher speed corners.

And no i wouldn't worry about the car starter. Dont idle

[timbob]

Driving with very little fuel in the tank is hard on a tank mounted fuel pump as it overheats. Save yourself the 2 or 3 hundred $'s to replace it by filling up at 1/4 full.

[BoostedNihilist]

This one is wrong. A modern fuel injected car with a standard transmission will not inject any fuel into the engine when you lift off the gas while coasting in gear. The drivetrain continues to turn the engine over, but there is no fuel going in. If you were to shift to neutral then it would start fuel flow again so that the engine will idle.

Speaking from experience, and to a degree logic, most modern manual transmissions do not know what gear state they are in, this is why a switch is wired in with the clutch pedal which is used to cut the starter wire... when you try to start the car in gear... without the clutch in it will not start.. if it knew it was in neutral, or in gear why would they put a redundant switch in?

Clearly, if you are coasting in a car, in gear, and the injectors are not injecting fuel, the air fuel ratio would not be sufficient to sustain combustion.. in other words, your car would die.. Depending on the fuel injection system this amount will change but it will never be zero. Starting an engine in the fashion described above (using the reciprocating mass to provide the compression stroke to start the combustion cycle) is very hard on engines.

'hypermiling' is a dangerous procedure where you conserve speed and fuel by operating outside normal procedures. I believe it is dangerous and the milage benefits you achieve will add up to larger maintenance costs down the road (tie rod ends, wheel bearings, starters) it really is a six of one situation.

Save yourself the 2 or 3 hundred $'

for the pump alone..

[Starsky]

This one is wrong. A modern fuel injected car with a standard transmission will not inject any fuel into the engine when you lift off the gas while coasting in gear. The drivetrain continues to turn the engine over, but there is no fuel going in. If you were to shift to neutral then it would start fuel flow again so that the engine will idle.

Speaking from experience, and to a degree logic, most modern manual transmissions do not know what gear state they are in, this is why a switch is wired in with the clutch pedal which is used to cut the starter wire... when you try to start the car in gear... without the clutch in it will not start.. if it knew it was in neutral, or in gear why would they put a redundant switch in?

Clearly, if you are coasting in a car, in gear, and the injectors are not injecting fuel, the air fuel ratio would not be sufficient to sustain combustion.. in other words, your car would die.. Depending on the fuel injection system this amount will change but it will never be zero. Starting an engine in the fashion described above (using the reciprocating mass to provide the compression stroke to start the combustion cycle) is very hard on engines.

You are correct that if you are coasting and there is no fuel being injected then the engine would die. BUT if you are coasting IN GEAR and there is no fuel being injected the engine will continue to turn because the wheels are turning and they are turning the driveshafts and the transmission which is turning the engine.

The engine does not need to know that it is in gear. All it needs to know is that the throttle is closed (which it does from the Throttle Position Sensor), that the engine is turning (the tach signal tells it this), and in some cases that there is airflow into the engine (the airflow meter does this). With this info the ECU knows that it can stop injecting fuel and there will be nothing noticeable to the driver. The second that you put your foot on the gas again the throttle position sensor tells the ECU that the throttle is no longer closed and fuel injection starts again.

[TheCheez]

2) I found a this one on Youtube.com -- Wait until you are nealy empty before refueling because if you have more fuel -- you have more weight. Other than doing price speculation on gas (in other words -- I'd fill up now rather than over a long weekend or when ever I think before gas is going to go up mentality) -- Lets take this one step further! Let's put your car into the "Utility" category.

Carry only enough fuel to get from Point A to Point B Plus an extra 45 minutes or whatever school rules are. This means your car carries less weight. If you do go to a gas station -- fill up only what need to get home in your tank and put the rest (say approx 40 liters) in a jerry can or gas container to take home...refuel using the jerry can or gas container before going on a round trip to and from work/destination.

COMMENT: I've never done this before (afraid my garage with fully loaded gas cans can be a hazard) -- but what effect do you think #2 would have??

This is pretty stupid. How much time and gas are you killing by stopping at the gas station every day? Screwing around with jerry cans and filling up at your home? Storing 40L+ of gas at your home?

I've heard people argue the other way too; that having a more empty tank causes more fuel to evaporate and vent out(and you should fill at 1/2 tank). Either way, we're talking about tiny adjustments in km's you can achieve from every tank.

As for your point 3. You can't go wrong keeping your car properly maintained. What you don't save in fuel will show up in long term serviceability.

Some of the principles of hypermiling are good. Some could easily fall under "obstructing traffic". Others are outright dangerous and more rational people will draw the line somewhere between time vs money vs health/safety. I've definitely slowed down, drive less and try to keep a more even speed now that gas is a significant expense.

[Dust Devil]

The price of gas is such a miniscule cost when it comes to operating a car this should be a non issue.

[Invertago]

Forget hypermiling... just find find one of those jacked up SUV, poke a wee little hole in their easily accessible fuel tank and tap into all the free gas you need

Tapping a typical hummer will keep my prius going for weeks!!! The beauty of it is that even if the owner catches you... odds are he's a tiny little guy anyhow who was just driving a hummer to compensate for other short comings



(not serious folks...)

[Captain X]

I hope you guys doing this at least do so in the slow lane. Some of us have somewhere to go and don't have all day to get there.

Big surprise! you and everyone else in Calgary is in a hurry to go no where

[Rowdy]

Starsky.. sorry to say.. but you're out of your mind on that one.

The ECU's do not and would never be programmed to cut fuel completly off during decel in gear. Thats just ridiculous and could cause numerous driveability and safety issues that the car manufacturers do not want.

MOST batch fired injection systems revert back to the idle sequence on decel. The sequential systems have an open loop thats based off of various sensor inputs to produce a smooth and efficient burn during deceleration.

The best ways to reduce fuel consumption are to avoid as many starts and stops and accelerations as possible. Pick a route that won't have you sitting idling away in traffic or stoping and starting at countless traffic lights. Better yet.. on those nice warm summer days.. Walk to the grocery store or post office if possible. Hell buy a bike!

[sstaurus]

re: idling vs. coasting

http://action.publicbroadcasting.net/ca ... 42810.page

I have confirmed to my satisfaction that the answer to my original question is, Yes, modern computer-controlled fuel injection will stop injecting fuel while coasting in gear, as the wheels will turn the engine and all of the accessory belts. I am glad I asked, because this was news to me.

I presented this same question over at a Consumer Reports forum, and their staff expert said:

"We have fuel meters that are tapped into the lines to read actual fuel consumption. Coasting in gear uses no fuel to speak of. Coasting in neutral still requires fuel to keep the engine running. The most efficient way is to come to a stop in gear for as long as possible and coast down hill in gear." [emphasis mine]

Any time you are engine braking, you are using no fuel to speak of.

If you have a Consumer Reports membership, you can view that thread here: http://dis...r-38aujohn
Post numbers 2 and 8 were the most informative.

By the way, no part of my consideration of this question involves turning off the engine at any time.

Thank you all . . .

[swede]

Hi There!

That thread about the Toyota Prius vs. Hummer kinda inspired me to write this and ask a couple of questions.

There is a new practice out there called hypermiling (meaning to drive in the most gas saving efficient way possible to squeeze the most out of every drop of gas).

I know most of you have heard about things like keeping your tires inflated right, getting a tune up, planning your trips/avoiding un-necessary trips etc., and basic things like coasting to a stop sign/red-light.

There are those who take it to the extreme however. I decided to experiment with it a bit this last 2 weeks using my 6 cylinder standard transmission 2002 Pontiac Pursuit.

I was just wondering if any of you would have the automotive expertise to comment on the following:

1) Instead of just coasting to a red light (especially when going down a hill) -- turn your ignition off...let inertia glide you there. Theory -- when coasting (with foot off accelerator) -- your engine still "idles" and uses up gas...so turn off the engine and use the built up inertia. If you are idling at a stop light -- you are using gas to get zero miles per gallon! Restart engine when light turns green.

If you have a leased car with an electronic odometer -- turning your ignition and power off allows you to coast significant distances that are not recorded on the odometer and thus saves you on leasing costs. It could build up over time.

If it looks like inertia won't get you to the stop sign -- push down on the clutch pedal so the friction from the engine/drive train etc. won't slow it down.

QUESTION: Isn't this hard on the starter motor and wear and tear?

2) I found a this one on Youtube.com -- Wait until you are nealy empty before refueling because if you have more fuel -- you have more weight. Other than doing price speculation on gas (in other words -- I'd fill up now rather than over a long weekend or when ever I think before gas is going to go up mentality) -- Lets take this one step further! Let's put your car into the "Utility" category.

Carry only enough fuel to get from Point A to Point B Plus an extra 45 minutes or whatever school rules are. This means your car carries less weight. If you do go to a gas station -- fill up only what need to get home in your tank and put the rest (say approx 40 liters) in a jerry can or gas container to take home...refuel using the jerry can or gas container before going on a round trip to and from work/destination.

COMMENT: I've never done this before (afraid my garage with fully loaded gas cans can be a hazard) -- but what effect do you think #2 would have??

3) Tune ups and changing air filter etc...I wonder what your cost of tune-ups are and changing oil filters/tires, ect...

Obviously it increases your gas milage but does that increase in gas milage offset the cost of the tune-up?? I remember owning a 1984 Trans-AM -- milage sucked so I got a tune up and it didn't seem to improve my milage much.

MyMeowCat

nice thoughts, mostly though you are gonna cost yourself on more wear and tear on starters and clutches and electrical components, not to mention it is illegal to coast or shut your engine off but I do it cause i live in bc and we have more than a few hills here which piss me off having to pay for gas to get down - so i do coast at times with the engine off (remember now, no power brakes or steering) and i shut my vehicle off at drive thrus and while waiting for lights to change. Precious little help, i would like to wring campbells drunken neck and then stuff his carbon tax where the sun dont shine.

[co-joe]

I hope you guys doing this at least do so in the slow lane. Some of us have somewhere to go and don't have all day to get there.

Big surprise! you and everyone else in Calgary is in a hurry to go no where

I think hybrids should come with big cushy rear bumpers so that if they are that concerned about mileage I can ram em out of my way. They'll save gas while I'm pushing, and I won't have to stop at each and every single red light. Ever notice how the lights in YYC are timed for 20-30 over the limit. Go the posted speed limit and you spend your whole day idling at lights. How much gas does that burn?

[MyMeowCat]

Thanks guys -- I didn't know that coasting in gear on a standard transmission fuel injected car does not actually use gas.

By doing some of those hypermiling things I managed to get my milage from 9.4 Litres/100 km down to 7.5 Litres/100 Km (according to my car's computer) and managed to get my fuel consumption down to approx $25/week instead of $55 per week (stop and go traffic in a city)...(includes things like taking shortest route possible, avoiding unnecessary trips, turn engine off at stop lights and traffic jams, etc.)

I saved so much money that I think I'll go on an un-necessary road trip

[g5]

Starsky.. sorry to say.. but you're out of your mind on that one.

The ECU's do not and would never be programmed to cut fuel completly off during decel in gear. Thats just ridiculous and could cause numerous driveability and safety issues that the car manufacturers do not want.

Actually, I'm with Starsky on this one. My car's computer registers pretty much 0 litres / 100km when decelerating in gear, whereas when leaving it in neutral there is always more consumption (depending on how fast you are travelling while at idle of course.)

The fact is, the engine doesn't need an air/fuel mixture at all as the wheels are turning the engine over there really is no combustion happening.

Turbo diesel is the way to go, and get a German (or any European) car. All the Jap cars I have had are reasonably efficient when comparing to American models, but nothing like a European car. I don't know what it is. (and I've had 6 Japanese cars, 3 American and 2 European, 3 4x4's, 3 diesels.)

[Pat Richard]

blah

[Sulako]

Go the posted speed limit and you spend your whole day idling at lights. How much gas does that burn?

For what it's worth, the gas engine on the Civic hybrid will generally cut out while you're waiting a traffic light, and you'll be running on the battery. It's designed so that everything, including a/c, can run just fine on the main battery. When the light goes green and you hit the accelerator pedal the electric motor provides initial acceleration while the gas engine lights up, and away you go. That's one thing I enjoy about the hybrid - when I'm sitting at a red light, at least I'm not having to burn half a tank of gas for the privilege of doing so. I'm sure the Prius has a similar feature.

When I think about it, why wouldn't that be a relatively easy thing to add to most cars / trucks? Just add another conventional battery at $100 and modify the electrical system to run off the battery while the engine is shut down. Even without an electric motor to start things off, it would only add maybe 1 - 2 seconds for the car to light up and start moving again.

[Starsky]

My 1998 3 series does this also. Not sure which car he figures doesnt do this.

I haven't found a credible reference to quote, but I understand that fuel injection cut on the overrun is a requirement of OBD regulations which have been around since the late 80's.

[Pat Richard]

I cant say if OBD1(pre 1995) vehicles do it, but OBD2(after 95) all do. OBD2 is an North American
requirement for all makes sold in Canada/US.