urban myth?

**jessman** · 04-10-2008, 12:19 PM

People tell me that having your car in 3rd gear rather then overdrive saves gas and gets you better mileage. Is this true?

**carsey** · 04-10-2008, 12:25 PM

Your car in any gear staying at a steady speed will save petrol. Soon as you accelerate it will go down.

I would have thought that the higher gear your in, and you are struggling to pick up speed it will use more gas.

**Jaxo** · 04-10-2008, 02:51 PM

I have heard that while driving downtown and relatively low speeds it's not a bad idea to be out of OD. Not for gas mileage but not having your tranny continue to shift when not really needing it. Myth? Not sure. I can see on the highway staying at the same speed OD is where you want to be.

Tumbleweed36 · 04-10-2008, 05:53 PM

On the road or highway, the OD will get the best mileage hands down. If you are doing driving where it has to shift all time, then forget the overdrive, because a steady 3rd gear would be best economy wise since you don't have to keep shifting up and down. That is my opinion.

**WereBo** · 04-12-2008, 08:10 AM

It depends on where you're driving, really. If you're motorway (freeway) or empty road driving and doing a constant speed, then use your highest gear for best fuel consumption. If you're town driving, then the highest gear where your revs are about 1/4 - 1/2 the range.

Vehicle manufacturers reckon the best fuel-use ratio is about 52-55 MPH, so if you drive at that speed in the highest gear and make a note of the revs. Keeping your engine at those revs, in whatever gear, should give you the best gas usage (approximately, it may vary, depending on road conditions - hills etc.).

A good tip for fuel economy is to keep the tyres inflated to the correct pressure. under-inflated tyres can knock up to 20% off the fuel economy, so can open windows - sunroofs etc.

**jessman** · 04-12-2008, 04:25 PM

open windows give less MPG than having your windows closed? HOw the heck does that work?

**WereBo** · 04-12-2008, 07:30 PM

It's to do with airflow and slipstream. It only makes a noticeable difference when you hit about 50MPH or over.

It's the same if you have a roof-rack mounted, they can add up to 40% fuel usage, especially if loaded with luggage etc. That's why you see folks covering the luggage with plastic sheeting etc. It not only keeps any rain off, it smooths the airflow somewhat.

Ellmist · 04-24-2008, 02:46 AM

Quote:

Originally Posted by WereBo

It's to do with airflow and slipstream. It only makes a noticeable difference when you hit about 50MPH or over.

It's the same if you have a roof-rack mounted, they can add up to 40% fuel usage, especially if loaded with luggage etc. That's why you see folks covering the luggage with plastic sheeting etc. It not only keeps any rain off, it smooths the airflow somewhat.

Actually thats a myth, having your windows open makes no real difference in gas milage unless you drive a larger SUV ( Larger SUVs Pocket more air. ) But even then it only adds an average of 5 cents a gallon to your fuel consumption budget. ^_^

* Watched way too much Mythbusters back in the day *

kendallt · 04-26-2008, 08:04 PM

when operating in overdrive the trans will constantly hunt gears to keep the engine in it's power band, shifting to high gear (4th on a 5spd) keeps it in the lower speed so it doesn't shift so often.

Unless radical advances have been made in transmissions, automatics when shifting from say 2nd to 3rd, 3rd-4th etc, don't go directly from one gear to another, they slowly release the 2nd gear clutches while simultaniously engaging the 3rd gear clutches. So for each gear change there is a time that each cluth is (gear) are engaged and slipping against each other. That's one of the reasons automatics tend to overheat at certain speeds. That's designed into them to provide smooth shifts. Aftermarket or performance valve bodies generally shift faster without as much overlap so can get better mileage.

Best way to determine the shift speed is to slowly accelerate on flat ground while watching the tach, or listening to and feeling the car, if it keeps shifting into OD at your normal in-town cruise speed you'll want to either hold it down a gear or speed up a little to keep it in OD.

I drive an explorer sport 4x4 as a work and play truck, and have played with it to improve mileage a bit, it's a manual, but lowest comfortable overdrive speed for it is 30 on flat and 35 on mild hills, which is where it starts to chug a bit and corresponds to the point the automatic would be shfting all the time.

There are tons of little things you can do to improve mileage, but due to driving habits and terrain, what works for one person isn't certain to work for another. Not even in the same vehicle, I can jump in my truck, drive all over the sate and get 25 mpg. My wife can jump in my truck and drive accross the state and can't get over 20mpg

sorry, got a little long on that one!

Ken

ZePhYrIuZ · 05-06-2008, 04:08 AM

depends on what speed you are driving though... if you are going 60kmh... or 35-40mph, a 5th gear would have better fuel efficency, overall, auto chews more fuel since if you step on more than 60% of your throttle, the car automatically changes the gear higher inorder for you to accellrate faster. if you have a car with a good aerokit like a racing body, you are gonna save heaps of fuel on the highway... as well as weight deduction on a car.

davez104 · 05-06-2008, 09:29 PM

Quote:

Originally Posted by Ellmist

Actually thats a myth, having your windows open makes no real difference in gas milage unless you drive a larger SUV ( Larger SUVs Pocket more air. ) But even then it only adds an average of 5 cents a gallon to your fuel consumption budget. ^_^

* Watched way too much Mythbusters back in the day *

You just busted your own bust

You say it doesn't make a difference but it makes a small difference

04-10-2008, 12:19 PM	#1 (permalink)
jessman TSF Enthusiast Join Date: Oct 2006 Posts: 501 OS: Vista 32 bit	urban myth? People tell me that having your car in 3rd gear rather then overdrive saves gas and gets you better mileage. Is this true?

04-10-2008, 12:25 PM	#2 (permalink)
carsey Moderator, TSF Articles Join Date: Aug 2006 Location: Hunwick, Co. Durham England Posts: 10,671 OS: XP Pro SP3 My System	Re: urban myth? Your car in any gear staying at a steady speed will save petrol. Soon as you accelerate it will go down. I would have thought that the higher gear your in, and you are struggling to pick up speed it will use more gas. __________________ Submit New Articles Here

04-10-2008, 02:51 PM	#3 (permalink)
Jaxo Design Team Member Join Date: Feb 2008 Location: Deming, NM Posts: 312 OS: XP SP2 & Vista	Re: urban myth? I have heard that while driving downtown and relatively low speeds it's not a bad idea to be out of OD. Not for gas mileage but not having your tranny continue to shift when not really needing it. Myth? Not sure. I can see on the highway staying at the same speed OD is where you want to be. __________________ Help TSF Fight Cancer! Web Developer Tools: Firebug for Firefox \| IE Developer Toolbar \| Run multiple versions of IE

04-10-2008, 05:53 PM	#4 (permalink)
Tumbleweed36 Asst Manager Hardware Join Date: May 2005 Location: USA Posts: 19,478 OS: XP Professional	Re: urban myth? On the road or highway, the OD will get the best mileage hands down. If you are doing driving where it has to shift all time, then forget the overdrive, because a steady 3rd gear would be best economy wise since you don't have to keep shifting up and down. That is my opinion. __________________ ---------- I don't receive email notifications of replies to subscribed threads. (Internet provider policy) Therefore, if I don't respond to your post within 24 hours, please send me a reminder PM and include the link to your thread.

04-12-2008, 08:10 AM	#5 (permalink)
WereBo Resident Village Idiot Join Date: Apr 2008 Location: SE London, UK Posts: 14,083 OS: Win-7, XP-Pro SP3 My System	Re: urban myth? It depends on where you're driving, really. If you're motorway (freeway) or empty road driving and doing a constant speed, then use your highest gear for best fuel consumption. If you're town driving, then the highest gear where your revs are about 1/4 - 1/2 the range. Vehicle manufacturers reckon the best fuel-use ratio is about 52-55 MPH, so if you drive at that speed in the highest gear and make a note of the revs. Keeping your engine at those revs, in whatever gear, should give you the best gas usage (approximately, it may vary, depending on road conditions - hills etc.). A good tip for fuel economy is to keep the tyres inflated to the correct pressure. under-inflated tyres can knock up to 20% off the fuel economy, so can open windows - sunroofs etc. __________________ I shall meet all of my deadlines directly in proportion to the amount of bodily injury I could expect to receive from missing them.

04-12-2008, 04:25 PM	#6 (permalink)
jessman TSF Enthusiast Join Date: Oct 2006 Posts: 501 OS: Vista 32 bit	Re: urban myth? open windows give less MPG than having your windows closed? HOw the heck does that work? Last edited by dai; 04-12-2008 at 08:02 PM. Reason: language

04-12-2008, 07:30 PM	#7 (permalink)
WereBo Resident Village Idiot Join Date: Apr 2008 Location: SE London, UK Posts: 14,083 OS: Win-7, XP-Pro SP3 My System	Re: urban myth? It's to do with airflow and slipstream. It only makes a noticeable difference when you hit about 50MPH or over. It's the same if you have a roof-rack mounted, they can add up to 40% fuel usage, especially if loaded with luggage etc. That's why you see folks covering the luggage with plastic sheeting etc. It not only keeps any rain off, it smooths the airflow somewhat. __________________ I shall meet all of my deadlines directly in proportion to the amount of bodily injury I could expect to receive from missing them.

04-26-2008, 08:04 PM	#9 (permalink)
kendallt Registered User Join Date: Feb 2007 Posts: 96 OS: win7-64	Re: urban myth? when operating in overdrive the trans will constantly hunt gears to keep the engine in it's power band, shifting to high gear (4th on a 5spd) keeps it in the lower speed so it doesn't shift so often. Unless radical advances have been made in transmissions, automatics when shifting from say 2nd to 3rd, 3rd-4th etc, don't go directly from one gear to another, they slowly release the 2nd gear clutches while simultaniously engaging the 3rd gear clutches. So for each gear change there is a time that each cluth is (gear) are engaged and slipping against each other. That's one of the reasons automatics tend to overheat at certain speeds. That's designed into them to provide smooth shifts. Aftermarket or performance valve bodies generally shift faster without as much overlap so can get better mileage. Best way to determine the shift speed is to slowly accelerate on flat ground while watching the tach, or listening to and feeling the car, if it keeps shifting into OD at your normal in-town cruise speed you'll want to either hold it down a gear or speed up a little to keep it in OD. I drive an explorer sport 4x4 as a work and play truck, and have played with it to improve mileage a bit, it's a manual, but lowest comfortable overdrive speed for it is 30 on flat and 35 on mild hills, which is where it starts to chug a bit and corresponds to the point the automatic would be shfting all the time. There are tons of little things you can do to improve mileage, but due to driving habits and terrain, what works for one person isn't certain to work for another. Not even in the same vehicle, I can jump in my truck, drive all over the sate and get 25 mpg. My wife can jump in my truck and drive accross the state and can't get over 20mpg sorry, got a little long on that one! Ken

05-06-2008, 04:08 AM	#10 (permalink)
ZePhYrIuZ Registered User Join Date: May 2008 Posts: 27 OS: xp sp2	Re: urban myth? depends on what speed you are driving though... if you are going 60kmh... or 35-40mph, a 5th gear would have better fuel efficency, overall, auto chews more fuel since if you step on more than 60% of your throttle, the car automatically changes the gear higher inorder for you to accellrate faster. if you have a car with a good aerokit like a racing body, you are gonna save heaps of fuel on the highway... as well as weight deduction on a car.