Correct Me If I'm Wrong...Increasing MPG Easily

[Drew99GT]

 Originally Posted By: parimento1

I mean if you are traveling at 90mph instead of 50mph, aren't you naturally getting more MILES out of a gallon of gas by travelling faster, and getting to your destination faster?

88 mph is a better speed for superb fuel economy!

 

[The Critic]

Here's why. Look at this chart for instaneous MPG at a particular speed.

 

[Quattro Pete]

Obviously Prius wasn't made with high speed driving in mind but it still does better than my car at 80 mph.

 

[ediamiam]

 Originally Posted By: parimento1

Wouldn't an easy way to get more MPG out of cars be to just raise the speed limit? I mean if you are traveling at 90mph instead of 50mph, aren't you naturally getting more MILES out of a gallon of gas by travelling faster, and getting to your destination faster?

wow..with thinking like that i was so sure you worked for the government

 

[parimento1]

LOL I do! But for the city gov't! (thank god not the EPA) I didnt realize just how fast the MPG go down with speed, it's really quite dramatic

 

[bdcardinal]

parimento1, i like your thought process. i regularly follow the idea of increased speed, but i dont care about gas mileage.

 

[Anduril]

Increased speed = increased RPMs and wind resistance. Your engine is working for a shorter amount of time, but doing more work within that time frame, which comes out to more fuel burned.

 

[Gary Allan]

Oh, you can manage no loss, but you have to project a "humidity field envelope" ahead of you. This will lower the air density and reduce drag. It's sorta like a warp field, but for terrestrial-atmospheric travel. The humidity field envelope has reached a high level of development and will be available soon wherever ....

 

[GROUCHO MARX]

Get a Scangauge, it will show you just how badly you're driving for fuel economy.

 

[asiancivicmaniac]

I have to try going 60 mph on my whole trip home in a few days and see what kind of gas mileage I get.

 

[Boatowner]

I am a 60 mph kind of guy, normally. I like getting 50 mpg in my Jetta and I can't do that at 70. However, time does factor into things and so I drove the limit or a little higher on my vacation with my 3 youngest last month. That meant a lot of 75 mph in Utah, Arizona, etc. and of course, California where speed limit signs are only there to give you reading material as you drive. So I averaged about 45 mpg on the trip. Not bad, but not what I would have gotten at a boring 60 mph. PS, I also hiked to the bottom of the Grand Canyon and back in one day and survived (South Kaibab Trail). Yes, I am bragging. At 56 I can do that.

 

[Audi Junkie]

DoE Chart:

 

[ekpolk]

 Originally Posted By: GROUCHO MARX

Get a Scangauge, it will show you just how badly you're driving for fuel economy.

As QP pointed out, time is not a factor in MILES per GALLON. It's MILES per GALLON, there's no TIME involved in that simple division. Now, if you want to INJECT time into the analysis, by all means get the ScanGauge-II, as Groucho recommends. I have one, and I often set it to display fuel flow, which is expressed in GALLONS per HOUR. If you set it to display GPH next to MPG and your speed, you WILL see the GPH increasing disproportionally (in fact, it does so exponentially) compared to speed, reflecting the unavoidable reality that the faster you go, the harder the car has to work to push through the air. Yes sir, respectfully, you are incorrect.

 

[labman]

How up to date is that chart? I have wondered with the better drag coefficients, if modern cars do better at higher speeds. Even if that chart is accurate for something, I did some figuring. 100 miles at 50 mph and 31 mpg = 2 hr and 3.2 gallons. 100 miles at 75 mph and 23 mpg = 1 1/3 hr and 4.3 gallons. So saving 1.1 gallons of gas costs 40 minutes or at $3/gal it pays $5/hr. What is your time worth? Maybe I need to work up some figures on my Scan Gauge. I consistently get about 33 mpg running 75-80 in my Cavalier, Ecotec and 5 speed. I wonder how much going slower would save? Going much faster might lead to expensive delays.

 

[The Critic]

 Originally Posted By: labman

How up to date is that chart? I have wondered with the better drag coefficients, if modern cars do better at higher speeds. Even if that chart is accurate for something, I did some figuring. 100 miles at 50 mph and 31 mpg = 2 hr and 3.2 gallons. 100 miles at 75 mph and 23 mpg = 1 1/3 hr and 4.3 gallons. So saving 1.1 gallons of gas costs 40 minutes or at $3/gal it pays $5/hr. What is your time worth? Maybe I need to work up some figures on my Scan Gauge. I consistently get about 33 mpg running 75-80 in my Cavalier, Ecotec and 5 speed. I wonder how much going slower would save? Going much faster might lead to expensive delays.

Look at the chart that I posted. It was from a 2010 Prius:

 

[chevrofreak]

I have a Scangauge in my 96 Crown Victoria P71. My most efficient speed is 35mph with overdrive engaged. At that speed, on level ground, I get 35-40mpg. As speed increases, it all goes downhill from there. At 45mph I'm lucky to get 31mpg, at 55 I'm doing about 28. At 75 I'm around 23.

 

[Kestas]

 Originally Posted By: parimento1

Correct Me If I'm Wrong...

You've been corrected.

 

[Trajan]

 Originally Posted By: Drew99GT

 Originally Posted By: parimento1

I mean if you are traveling at 90mph instead of 50mph, aren't you naturally getting more MILES out of a gallon of gas by travelling faster, and getting to your destination faster?

88 mph is a better speed for superb fuel economy!

Only if you have Mr Fusion handy.

 

[sciphi]

With the ScanGauge in my 99 Buick LeSabre, the most efficient speed is 62 mph. That puts the engine in a good torque band at a miserly ~1600 RPM. I've consistently gotten 35-37 mpg highway tanks at that speed. That's also not letting the speed drop below 60 mph on the hills and letting the car coast as much as is safe down the backside. Going faster is a nightmare. At 70 mph I get ~31 mpg, and at 75 28-29 mpg is good.

 

[labman]

 Originally Posted By: chevrofreak

I have a Scangauge in my 96 Crown Victoria P71. My most efficient speed is 35mph with overdrive engaged. At that speed, on level ground, I get 35-40mpg. As speed increases, it all goes downhill from there. At 45mph I'm lucky to get 31mpg, at 55 I'm doing about 28. At 75 I'm around 23.

 Originally Posted By: sciphi

With the ScanGauge in my 99 Buick LeSabre, the most efficient speed is 62 mph. That puts the engine in a good torque band at a miserly ~1600 RPM. I've consistently gotten 35-37 mpg highway tanks at that speed. That's also not letting the speed drop below 60 mph on the hills and letting the car coast as much as is safe down the backside. Going faster is a nightmare. At 70 mph I get ~31 mpg, and at 75 28-29 mpg is good.

Interesting such a big difference. We have a long drive to a wedding next weekend. I may see what the Scan Gage on my Cavalier does at different speeds.