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Generally, above the 'sweet spot' of 40-50 MPH, going faster costs you mileage, as the wind resistance increases and the engine works harder. Acceleration is the other main drag.

I'm sure someone with more time and better eloquence will come post a much better explanation shortly. :)
 

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8) In respect to higher speeds increasing fuel consumption, the Prius is no different from 'old fashioned' cars. Even though the Prius has the best design for reducing wind resistance, the higher the speed the lower the MPGs.

In freeway driving when I've been able to sustain ~70 MPH, my 2004 Prius achieved 50-55 MPG. I just traded the 2004 for a 2007 Touring Edition, so I don't have a read on the new Prius yet. Around Dallas, my MPG usually has been 40-45 MPG with 'stop'n'go' city driving.
 

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Zaxxon said:
Generally, above the 'sweet spot' of 40-50 MPH, going faster costs you mileage, as the wind resistance increases and the engine works harder. Acceleration is the other main drag.

I'm sure someone with more time and better eloquence will come post a much better explanation shortly. :)
There's not really a "sweet spot' in the 40-50mpg range.

Unfortunately, I can't find/recall where the chart I have is. Anyway, the 'sweet spot' is actually around 25mpg. That said, anything in the sustained 35-45mph range will result in excellent mpg.
 

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wind resistance increases by the square of the speed. For most cars, the "tipping point" where fuel economy will get worse as you increase speed is around 55mph.

http://auto.howstuffworks.com/question477.htm

I know that Wayne at http://privatenrg.com/ has a PalmOS program to calculate Prius fuel efficiency based on vehicle speed and wind direction, but I don't have the table of fuel economy figures generated from it handy (nor do I own a Palm).
 

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efusco said:
Unfortunately, I can't find/recall where the chart I have is. Anyway, the 'sweet spot' is actually around 25mpg. That said, anything in the sustained 35-45mph range will result in excellent mpg.
I've only had mine for just over a week, so I could be off-base. I do know that whenever I'm in the 40-50 range and I glance at my MFD, I'm in the 50s-70s in MPG. I could be misremembering this as sustained when it's actually a slight deceleration, though.
 

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mrv said:
wind resistance increases by the square of the speed. For most cars, the "tipping point" where fuel economy will get worse as you increase speed is around 55mph.

http://auto.howstuffworks.com/question477.htm

I know that Wayne at http://privatenrg.com/ has a PalmOS program to calculate Prius fuel efficiency based on vehicle speed and wind direction, but I don't have the table of fuel economy figures generated from it handy (nor do I own a Palm).
He has developed a PC program that does the same and more and should be available soon on his website.
 

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I've seen another chart that shows 37 mpg is theoretically the best (at 86°F if I recall). But my experience is much different. I've drivent at 40 mph for a long ways and watched the fancy screen, and I ain't getting ultra high mileage. I've been amazed at reports of 60+ mpg from folks on here. Maybe it's too darn hilly here.
 

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DanMan32 said:
I agree, 80 MPG is extremely optimimistic even for 37 MPH.
I might try driving 37 MPH home sometime when traffic is light and see what I get.
Are you sure you're up to speeding up that much? :wink:
 

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Hep said:
DanMan32 said:
I agree, 80 MPG is extremely optimimistic even for 37 MPH.
I might try driving 37 MPH home sometime when traffic is light and see what I get.
Are you sure you're up to speeding up that much? :wink:
Well, if your implication of me being a grampy driver were true, I'd be getting 80MPG now, wouldn't I? :wink: Then I could report the validity (or invalidity) of that chart.
 

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MtnTraveler said:
I've seen another chart that shows 37 mpH is theoretically the best (at 86°F if I recall). But my experience is much different. I've drivent at 40 mph for a long ways and watched the fancy screen, and I ain't getting ultra high mileage. I've been amazed at reports of 60+ mpg from folks on here. Maybe it's too darn hilly here.
Note change in bold above!
 

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DanMan32 said:
Hep said:
DanMan32 said:
I agree, 80 MPG is extremely optimimistic even for 37 MPH.
I might try driving 37 MPH home sometime when traffic is light and see what I get.
Are you sure you're up to speeding up that much? :wink:
Well, if your implication of me being a grampy driver were true, I'd be getting 80MPG now, wouldn't I? :wink: Then I could report the validity (or invalidity) of that chart.
I thought that Hep would have figured it out by now. DanMan32, DanMan32 (bold added). He used to be known as DanMan32mph :lol:

And lets determine mathematically DanMan32's actual speed. On his 5/16/2006 post he states he's gotten 55.4 mpg. Now looking at the chart we see two possible points of intersection, 63.5 mph or about 5 mph. We also know he drives on Alt 19, so you can forget about that 63.5 point. Therefore, we have determined that his average speed is 5 mph. :D The really scary thing is that the walkers who are passing him can't hear the Prius in stealth mode. But then again, everybody is lucky that DanMan32 has a great sense of humor.
 
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