A reason to drive the speed limit

[rwarn17588]

The number on the left from my Honda Insight's dashboard is the miles per gallon. The number on the right is the total number of miles driven from fill-up until the gas light came on.

Most of the driving was on U.S. 60 going from Oklahoma to Sikeston, Mo., then on Interstate 57 to southern Illinois. There was wasn't a tailwind, and I did use the air conditioner.

I simply observed the speed limit wherever I was driving. I bested my all-time high for a tankful by more than 80 miles. It took a day and a half of driving to finally get the gas light to come on.

Driving the speed limit is yet another way to reduce oil consumption in the United States.

[cannon_fodder]

That's awesome.  If you get the federal 48.5 cents per mile and get reimbursed for work... driving a lot you would make some SERIOUS money. []

If not, you still saved yourself some cash AND me, by using less gas you help lower prices.  So thanks.

[tulsacyclist]

Yeah, I've been really trying to keep that in mind as I'm driving. Over the past couple weeks I've began driving less and less aggressive. Sometimes when I'm going 65 it seems like I'm going sooo very slow - but I'm getting used to this speed limit thing.

[inteller]

implying that driving the speed limit at al times saves gas is a FALLACY.

so you are saying that I get the best gas mileage if I drive 25 on neighborhood streets?  I beg to differ.

In fact, I get the same gas mileage going 80 that I get going 65 so this is pure myth.

gas mileage has more to do with final drive gears than how fast you are going.  it has nothing to do with speed, it has to do with how low you can keep your RPMs.

[Ed W]

"gas mileage has more to do with final drive gears than how fast you are going. it has nothing to do with speed, it has to do with how low you can keep your RPMs."

Rolling resistance (friction) increases linearly with speed.  Drag increases with the square of the speed.  So in general terms, if you double your speed, drag quadruples.  Overcoming friction and drag require more power, regardless of rpms.  

There ain't no such thing as a free lunch.

[rwarn17588]

Obviously, inteller, when I was driving across Missouri, I wasn't driving 25 mph on U.S. 60. Duh.

From FuelEconomy.gov:

"While each vehicle reaches its optimal fuel economy at a different speed (or range of speeds), gas mileage usually decreases rapidly at speeds above 60 mph.

"As a rule of thumb, you can assume that each 5 mph you drive over 60 mph is like paying an additional $0.20 per gallon for gas.

"Observing the speed limit is also safer."

http://www.fueleconomy.gov/feg/driveHabits.shtml

[inteller]

quote:Originally posted by Ed W

"gas mileage has more to do with final drive gears than how fast you are going. it has nothing to do with speed, it has to do with how low you can keep your RPMs."

Rolling resistance (friction) increases linearly with speed.  Drag increases with the square of the speed.  So in general terms, if you double your speed, drag quadruples.  Overcoming friction and drag require more power, regardless of rpms.  

There ain't no such thing as a free lunch.

yeah sure, if you are driving a box.  Some of us have things such as aerodynamics.  My car is aerodynamically limited to 145.  and going from 65-80 is HARDLY doubling my speed.  perhaps thats why i get the same gas mileage.

[inteller]

quote:Originally posted by rwarn17588



"As a rule of thumb, you can assume that each 5 mph you drive over 60 mph is like paying an additional $0.20 per gallon for gas.

yeah, that's just your good ole government spreading propaganda to justify lower speed limits to keep road wear and tear to a minimum.

so if it were up to the EPA, the speed limit would be 60 everywhere....that is absolutely ridiculous.

[swake]

quote:Originally posted by inteller

quote:Originally posted by Ed W

"gas mileage has more to do with final drive gears than how fast you are going. it has nothing to do with speed, it has to do with how low you can keep your RPMs."

Rolling resistance (friction) increases linearly with speed.  Drag increases with the square of the speed.  So in general terms, if you double your speed, drag quadruples.  Overcoming friction and drag require more power, regardless of rpms.  

There ain't no such thing as a free lunch.

yeah sure, if you are driving a box.  Some of us have things such as aerodynamics.  My car is aerodynamically limited to 145.  and going from 65-80 is HARDLY doubling my speed.  perhaps thats why i get the same gas mileage.

Dude, that is so cool, I wish my car could do that. Wow.

[rwarn17588]

Leave it to some folks to find a cloud amid a silver lining.

[inteller]

quote:Originally posted by rwarn17588

Leave it to some folks to find a cloud amid a silver lining.

wow,  I just completed a trip of 300 miles each way, I got the SAME gas mileage going 80 one way that I got going 70 the other.....the EPA is going to have a cow!

[cannon_fodder]

I've never done a scientific study, but when I got 80-85 in Oklahoma I get 24mpg and when I go 70 in Iowa I get 27mpg.

Many cars from the early 2000's are geared to get the best gas mileage from 65-75mph.  After that they decline rapidly as they just do not gear them to run efficiently at those speeds.

/what I've noticed anyway.

[rwarn17588]

My wife's Scion did 41 mpg driving the speed limit this past weekend and 37 mpg when was hauling a** on the interstate.

So, between cannon fodder, her and me, we saw our miles per gallon drop 10 percent or more when going faster.