Coasting in neutral is dangerous, illegal in most places, and in a fuel injected car, uses more gas than coasting in gear. Simple as that. Don't do it.
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The (Don't Yawn!) Fuel Economy thread!
- Thread starter dazzer21
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GroundLoop
macrumors 68000
I drive a 2007 Toyota Camry Hybrid. I get 38 mpg combined driving. I also keep the air conditioning on all of the time. In fact, I am not even sure if the windows work.
I usually get about 550 miles to the tank (fill up at 1/8th)
Hickman
I usually get about 550 miles to the tank (fill up at 1/8th)
Hickman
dmr727
macrumors G4
Heh! What makes you think it's a plane? Could be a boat! 😉
It's just a Cessna. Nothing interesting.
gnasher729
Suspended
Please mention which country you are in. US gallons are not the same as UK gallons, and US miles per gallon are not the same as UK miles per gallon.
My mom has a Range Rover Sport HSE (nonsupercharged 4.4 V8)
It gets 14.0 city. 14.1 highway. The dealer is looking to do some software update or something.
Ridiculous.
It gets 14.0 city. 14.1 highway. The dealer is looking to do some software update or something.
Ridiculous.
IJ Reilly
macrumors P6
However, with a manual transmission, taking your foot off the accelerator induces engine breaking, so while you might use less fuel, the car will slow to a stop far more quickly.
MacNut
macrumors Core
Artofilm
macrumors 6502a
If a car cuts off the fuel, that is called a stall.
A car cannot run without fuel.
You are talking about idle. Which uses less gas to run.
I have noticed people are driving a lot differently on roads.. Seems to be for the better. Accidents are down too. WIN WIN
Yes, that is true. I'm not sure what uses more gas, coasting in neutral or coasting in gear and blipping the throttle as needed (any difference is probably negligible) but coasting in neutral is still dangerous and shouldn't be done.
But engine braking can be good though. For example, there's a hill near my house, speed limit is 40. When I'm going down it, I'll start at the top at 40 in 4th, and just coast to the bottom with no brakes, still in gear, and my speed might increase to about 42 or 43. A quick tap of the brakes at the bottom, and I'm back down to 40. I'm putting much less wear on my brakes than the guy who rides the brakes all the way down. So, depending on the roads and traffic, the increased engine braking can be a good thing.
A stall is not cutting off fuel. A stall is when the engine speed slows down enough that the engine can't move the car, and it stalls. In my above example, when I go down that hill in gear and coasting, my car doesn't use a drop of fuel. The movement of my wheels are enough to keep the engine spinning fast enough to prevent a stall. If I keep coasting and never give it gas, and reach level ground or uphill, then the car will slow down enough that the engine can't keep up, then it'll stall. But merely cutting off fuel does not cause the engine to stall.
Idle is when an engine is spinning while not in gear. That uses fuel to keep the engine spinning, and yes, if you cut off fuel then, it'll stall since the momentum of the wheels won't keep it spinning. But in a manual transmission in a fuel injected car, coasting while in gear uses no gas.
Yea, its quite peculiar. It's rated at 12/18 so I guess its doing good in the city and not so good on the highway.
The dealer mentioned that this issue was somewhat common on 2005 LR3's and Range Rover Sports due to something with the software, as well as random suspension fault messages. But her's is an 07 so who knows. We're bringing it in tomorrow to have it checked out. At first we didn't notice. Then it we questioned why it always said ~14mpg for fuel economy, then we figured it must be something wrong with what ever calculates that, but then eventually we did out the math using the tripodometer the old fashioned way, and it still came out to 14mpg.
Hopefully its just a simple software glitch. My mom uses premium, it seems to run soundly, no check engine lights indicating bad engine sensors. Who knows...
IJ Reilly
macrumors P6
With an automatic transmission, I'd agree taking the car out of gear is dangerous, but it's perfectly okay with a manual. Engine braking is useful if you want or need to save your brakes, but I would not make a habit of it, as it trades off brake wear for clutch wear.
Rodimus Prime
macrumors G4
Taking the car out of gear even on a manual can be dangerous because it does not way to control the speed.
As for coasting just put the car in a higher gear and keep the RPM above idle. 5th/6th gear is good down to about 20 MPH.
And yes I am taking as a manual driver. As long as one is in the over drive gear (aka 5th or 6th depending on the car) it is the same as a Auto in part of getting better gas mileage.
kellen
macrumors 68020
2000 Jeep Cherokee. Metallic grey in color, I-6, the great boxy bodystyle. I love it and gas isn't making me give it up. Gets around 18-20 combined, but lately been around 14. Think its because of the summer gas and the AC, plus all city driving lately. Get a little higher because I am going off of the trip odometer and I have 30" tires, so its like 5% greater.
I have changed my driving habits, consolidate driving and try not to drive as much. Plus pay more attention to how heavy I am on the skinny pedal.
But I love it. Hope to keep it forever, as the I-6 is known to run forever and the AW-4 tranny is bulletproof. The electrical and body, well thats another story.
I have changed my driving habits, consolidate driving and try not to drive as much. Plus pay more attention to how heavy I am on the skinny pedal.
But I love it. Hope to keep it forever, as the I-6 is known to run forever and the AW-4 tranny is bulletproof. The electrical and body, well thats another story.
It does NOT wear your clutch any faster unless your clutch is already slipping or, for some reason, you keep your foot slightly pressed on the clutch pedal.
Outside of a slipping clutch the only time you are adding wear to a clutch is when starting from a stop and during shifts, the rest of the time the disk and flywheel are turning at the same speed, no wear.
On a big truck a clutch is expected to last well over 400K miles yet the engines produce over 400lb/ft of braking torque with the engines brakes on full power. If engine braking caused wear they wouldn't last nearly as long.
Our family has four Jeeps, so forget about fuel economy. Our most 'fuel efficient' car is my dad's 2001 BMW 330ci, which averages out 20 mpg between city and highway, I think. The Jeeps are in the low teens.
Sly
macrumors 6502
Engine breaking (coasting in gear) is actually a very efficient way of slowing a car down. It uses a lot of energy compressing the air in each cylinder 1000's times a minute, which in turn slows the car down pretty quickly, especially in a low gears. This can be a very useful technique when intentionally keeping your speed manageable on a steep down hill stretch. However as far as economy is concerned coasting in gear is less efficient that coasting out of gear as the engine breaking effect slows the car down loosing momentum which has to be regained by acceleration, using far more fuel than coasting out of gear, its basic physics.
If coasting out of gear, I would suggest putting your foot on the clutch, pre-selecting the gear needed for the road ahead, then coast with your foot on the clutch. This does two things, it reduces the components spinning in the gear box, so reduces friction for more economy and it allows you to quickly regain drive if needed by just dumping the clutch.
If coasting out of gear, I would suggest putting your foot on the clutch, pre-selecting the gear needed for the road ahead, then coast with your foot on the clutch. This does two things, it reduces the components spinning in the gear box, so reduces friction for more economy and it allows you to quickly regain drive if needed by just dumping the clutch.
Coasting out of gear is dangerous, because if you need to hit the gas and quickly get out of the way to avoid something, you won't be able to. That's why it's illegal in some places
well, i'm probably going to get flamed but i'm the proud owner of a toyota tacoma 4x4 doublecab. I get about 21 mpg for mostly city driving. i drive much slower now, trying to keep RPMs around or under 2000. I also make multiple stop drives meaning I'll wait to visit stores and hit them all on the same day (stay-at-home Dad running my own biz so i grocery shop alot 🙂 I also shut my engine off at certain lights which I know can be long.
I've had thoughts of totally going the opposite direction and getting the Prius, but screw it. The last 2 fatal accidents around my house have been - small cars. At least in a truck, me and the boys will have a higher chance of survival and for that, i'm willing to pay for it (to a certain extent of course 🙂
Plus, i live in this place called Canada and i'm quite interested to hear what all the ppl buying smaller cars instead of their trucks/SUVs, will have to say if we have another brutal winter. They'll probably be expending almost the same amount of gas as I'll be using to get out of snowdrifts or just driving around...spinning tires etc.. I know I sure appreciated my 4x4 last winter. That's not meant to come with attitude, but just a plain fact.
I do applaud increasing hybrid technology. I actually look forward to the day when I can change the engine in my truck for a hybrid engine. I know Neil Young is working with a guy on a system to change engines. If anyone can successfully invent this, it could be a massive business and plus, it's just smart to do.
My wife's lease is up next year and i'm pleading with her to buy a hybrid model. She drives alot for work so it will be a larger car or suv type (nothing massive though).
cheers,
Keebler
I've had thoughts of totally going the opposite direction and getting the Prius, but screw it. The last 2 fatal accidents around my house have been - small cars. At least in a truck, me and the boys will have a higher chance of survival and for that, i'm willing to pay for it (to a certain extent of course 🙂
Plus, i live in this place called Canada and i'm quite interested to hear what all the ppl buying smaller cars instead of their trucks/SUVs, will have to say if we have another brutal winter. They'll probably be expending almost the same amount of gas as I'll be using to get out of snowdrifts or just driving around...spinning tires etc.. I know I sure appreciated my 4x4 last winter. That's not meant to come with attitude, but just a plain fact.
I do applaud increasing hybrid technology. I actually look forward to the day when I can change the engine in my truck for a hybrid engine. I know Neil Young is working with a guy on a system to change engines. If anyone can successfully invent this, it could be a massive business and plus, it's just smart to do.
My wife's lease is up next year and i'm pleading with her to buy a hybrid model. She drives alot for work so it will be a larger car or suv type (nothing massive though).
cheers,
Keebler
Did the calculation
I managed to eek a few more miles out of my Corsa and got an overall mpg figure of 50.2. According to the figures I can find, combined should be 44.3. I thought there'd be a bit more of a differential, but hey, it's a saving...
I managed to eek a few more miles out of my Corsa and got an overall mpg figure of 50.2. According to the figures I can find, combined should be 44.3. I thought there'd be a bit more of a differential, but hey, it's a saving...
wordmunger
macrumors 603
I have a Prius and average about 47 MPG without doing any special driving tricks. My 1994 Plymouth Voyager, which I drive as little as possible, gets about 23.
IJ Reilly
macrumors P6
Dangerous? I think that's nonsense. The car is out of gear every time you shift. If you keep your foot on the clutch pedal and your hand on the shifter, then you're not sacrificing any meaningful amount of control. And I'm not talking about coasting for miles, just the last couple hundred feet before an off-ramp, and down the ramp if the situation allows. As for the fuel economics of coasting vs. using high gear, I'm open to hard evidence that one or another is better. Lacking any, I'd have to assume that covering ground at engine idle burns the least amount of fuel possible.
BTW, I assume most manual transmission drivers coast all the time, probably every time they turn a corner.
Sure it does, if you downshift, which really the only effective way of using engine braking. Some manual transmission drivers do this virtually every time they come to a stop, which is certainly going to promote clutch wear because they're shifting one more time than necessary per stop.