How to Save Money on Gas

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bobcat2
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How to Save Money on Gas

Post by bobcat2 »

Quit driving so damn fast. 8)
Air resistance increases the faster you travel, which might lead you to think that higher speeds always require more fuel. However, your car's engine is designed for maximal efficiency in converting fuel into motion when you drive at higher speeds. As a result, the typical car gets much better gas mileage if you drive it at 45 mph instead of 15. However, at speeds above 60 mph, the wind resistance becomes a dominant factor, and miles per gallon for most cars starts to decline significantly if you drive faster than 60....

Driving more slowly should also reduce your carbon footprint and any other pollutants by the same amount indicated in the second column above, and should lessen the likelihood and severity of collisions. And most urban highways prohibit speeds over 65, so you're exposing yourself to risk of fines and higher insurance rates if you drive at higher speeds. Even without these added considerations, however, I would think that many people, if they knew that the immediate financial rewards were on the order of the numbers given above, might choose to drive more slowly. In which case, it is perhaps a public service to help call such numbers to people's attention.

Which, in case you were wondering, is why I wrote this post.
Below is a link to this most excellent article by James Hamilton at Econbrowser.
Link:
http://www.econbrowser.com/archives/200 ... e_mon.html

Bob K
Last edited by bobcat2 on Sun Jun 22, 2008 9:05 am, edited 1 time in total.
In finance risk is defined as uncertainty that is consequential (nontrivial). | The two main methods of dealing with financial risk are the matching of assets to goals & diversifying.
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Grandpaboys
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Post by Grandpaboys »

Live in a small town. Everything I need is within a 4 mile round trip.
Good Day | GP
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Midpack
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Post by Midpack »

FWIW I am actually getting 30-45 miles more on a tank of gas now. I know because a) I fill up when my nearing empty idiot light comes on so I am always aware of the odometer reading when it comes on, and b) I have calculated my mpg on a few tanks recently and gotten better mileage than in the past. All I changed:

- I am driving the speed limit (used to drive at least 10mph more most of the time)
- I am using cruise control wherever possible, not just on highways
- I am paying attention to keeping my tires at proper pressure (used to check infrequently)
- I am trying to put the car in neutral at stoplights, but frankly I forget to do it about 90% of the time (so far).

I am getting 2-3 mpg more mileage and my wife is getting 3-4. A nice change, no sacrifice at all really...
You only live once...
INDUBITABLY
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Post by INDUBITABLY »

Yup, drag increases with the square of velocity, all other things being equal. Exactly where the sweet spot is depends on how your car or truck is geared -- the manual for my Subaru indicates 55 mph.
"Ah ha! Once again, the conservative, sandwich-heavy portfolio pays off for the hungry investor!" - Dr. Zoidberg
gassert
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Post by gassert »

You car doesnt burn any less fuel in N at a light than D. Putting in N would be fine on a long downhill because there's less rolling resistance, but coasting in N or D (or at idle) is about the same fuel consumption.
bolt
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Post by bolt »

Midpack wrote:FWIW I am actually getting 30-45 miles more on a tank of gas now. I know because a) I fill up when my nearing empty idiot light comes on so I am always aware of the odometer reading when it comes on, and b) I have calculated my mpg on a few tanks recently and gotten better mileage than in the past. All I changed:

- I am driving the speed limit (used to drive at least 10mph more most of the time)
- I am using cruise control wherever possible, not just on highways
- I am paying attention to keeping my tires at proper pressure (used to check infrequently)
- I am trying to put the car in neutral at stoplights, but frankly I forget to do it about 90% of the time (so far).

I am getting 2-3 mpg more mileage and my wife is getting 3-4. A nice change, no sacrifice at all really...
Me too.........especially using the CruiseControl as a means of acceleration despite looking like i'm standing still on most highways w/people still doing 70-80mph,.. hey its something! Good luck!
INDUBITABLY
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Post by INDUBITABLY »

For anyone looking for more information on techniques to improve fuel economy, the Wikipedia page is quite helpful. Also worth checking out is one of the "hypermiler" forums such as cleanmpg.com if you want to ask questions and things like that.
"Ah ha! Once again, the conservative, sandwich-heavy portfolio pays off for the hungry investor!" - Dr. Zoidberg
cdelena
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Post by cdelena »

I do not drive any differently... sometimes I exceed the limit and do often make driving decisions based upon making the light, getting around the difficult driver, getting where I want to go quickly, etc.

If I change my habits to conserve fuel (I do know how as I am very familiar with autos) it will save me about $8 a month and it is just not a good value for me.
bill99
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Survival is still Job One

Post by bill99 »

In dense, urban/suburban traffic (the kind I'm in most of the time), my first priority is trying to keep some space around my car -- ahead, to the sides, and behind me.

Too many loose screws driving, drivers not paying attention, not signalling turns, yakking on their cells, driving in your blind spot (for fun?), glued to your rear no matter how fast you drive, or driving slow in the left lane, etc., etc.

So job one is "separating" -- keeping space around you when you can, and having escape options pretty much all the time.

Once you've got that done, then:

1. Tire pressure, sure. If we all did it, we'd save a lot.
2. Drive smoothly, when you can.
3. Drive with the flow; you'll know because you won't be passing most cars, and most cars won't be passing you. Speed DIFFERENCE is one of the big risks. You don't want a lot of drivers blowing by you 20mph faster, while they're looking down at their cellphone. :-)
4. Cruise control, sure. Where you can.

Final comment: Be a little careful with the hypermiling in traffic. Example One hypermiler mentioned he lets his hybrid get up to 65 on downhill stretches (Interstate), and then let's it drop down to 50 on the uphill parts, before accelerating. On an uphill, that drop from 65 to 50 can happen pretty quick, I'm guessing with no brake lights, which may cause the following driver to brake hard or swerve. Not clever.

A little common sense never hurts.
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DRiP Guy
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Post by DRiP Guy »

cdelena wrote:I do not drive any differently... sometimes I exceed the limit and do often make driving decisions based upon making the light, getting around the difficult driver, getting where I want to go quickly, etc.

If I change my habits to conserve fuel (I do know how as I am very familiar with autos) it will save me about $8 a month and it is just not a good value for me.
I understand what you mean, but it doesn't have to be all or nothing. For instance, if you leave a tiny bit earlier, then you aren't pressed to 'make time', which means you can decide to just chill in the slow lane a bit more a the speed limit versus fast lane where you need to do five or ten over, or you are obstructing the flow... I have been a go-go rush hour driver for almost thirty years, and I get frustrated by brainless 'wanderers' or 'tourists' or 'lolly-gaggers' on cell phones, but it is important to remember you are going to have a lot more of those type of 'obstacles' as these high prices continue -- it's probably better to try to adapt a bit, rather than stick out like a sore thumb.

I took a 1500 mile trip recently, and I think the whole time, which I spent at the speed limit, I got passed maybe three or six times by people; where in the past, frequent trains of fifteen cars going 85 mile/hr was the norm.
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