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Discussion Starter · #1 ·
I will be the first to admit that mine is not a scientific study, but thought it might be of interest. I now have driven 40,000 miles, having kept track of all gas purchases. During the first 35,000 miles, while I tried to drive for good gas mileage, I typically drove at 65mph when conditions allowed. I had a lifetime average during that period of 52.389mpg. Then, during the last 5,000 miles, I kept my freeway speeds down around 55-57mph most of the time, and my average for that period alone is 56.86. (Total lifetime average is up to 52.91). I live in So. California, so I have the benefit of warmer temperatures, and I use the a/c, defrost, heat etc. sparingly. Most of the time the computer shows a slight difference in mileage on individual tanks, but I figure over the long haul my record keeping is pretty accurate.
By the way, I keep to the far right lane unless I need to pass a slower vehicle when I am driving at the lower speeds. That doesn't avoid entirely the ire of some motorists, most notably those in gas guzzling suv's and pickup trucks. But then, that's no surprise, is it? I have also been passed by many a Prius! Hey, folks, I bought mine for economy of operation, and if slowing down a little can produce these kinds of results, I'm willing!
 

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Discussion Starter · #3 ·
Experiment

So far, it hasn't bothered me to annoy anybody, but also, the Prius drivers just keep going in the other lanes. Must be kinder and gentler people! The minimum speed limit on freeways here in the warmth of California is 45mph. Trailer trucks and autos pulling trailers are limited to 55mph, and must drive in the right lane except to pass. If I am doing 55-57 and staying to the right with the big rigs, then it is up to the guy who wants to do 70, cutting in and out of lanes, to avoid the right lane altogether.
 

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I have lowered my speed on the 91, 5, 405, and 55 to 65mph even though everyone else is going 70mph, traffic permitting. :)
But lowering it from 70 to 65 really helped my mpg's a lot. They went from low 40's to high 40's now that I drive slower on the freeways.
 

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Test I did: Same exact trip, 3 times, in almost exact same weather conditions. Only variable was speed. 100% freeway trip.

Cruise set at 75 or 80 38mpg

Cruise set at 65 52mpg

Cruise set at 55 61mpg
 

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Speed vs mileage

It always intrigued me, ever since I found this forum, that the fuel economy in the US was much less on average that what I was achieving here in NZ. I first got the car last winter and it has consistently been in the high 50s to low 60s.

Now I realize that, like any other car, the consumption suffers when the speed increases. Our highway limit is 100kph (just over 60 mph) and surface streets 50kph. Pegging the cruise control at 95 or so is perfect as it gets me past the big rigs and I don't compete with the petrol heads in their V8 behemoths or the Subaru WRX turbo guys who HAVE to pass everything on the road.

Life is so much better when you choose not to compete in this insane road race. :roll:
 

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Speed vs mileage

I meant to add to the last post that there was an economy run here a few months ago and the first and second place went to Prii, the winner did 4.04 l/100 km (70 mpg!!) all at legal highway speeds, with driver and passenger.
You beaut!! :D
 

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I believe they said that for every 5 MPH above 55 MPH you lose 15% fuel economy. I usually drive 60 (and yes I am in the far right lane if 70 mph is the limit). If I am in a rush then I drive 70. I still have the F250 (try to save gas mentality). Driving 60 instead of 70 saved me 3 mpg (16 vs 13 mpg) in that big truck. I have not tested my Prius to see what eh MPG dif is.
 

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Driving speeds

I drive just a few MPH over the speed limit in most circumstances. I've had the best mileage at between 55 and 60 mph, where I will often peak over 50mpg even during these colder months, and can average just a tad over 50mpg in gentle rolling hills at that same speed. However, I drive around 73-75 (depending on traffic) on the highway and that drops the average down to just over 40. So there is a huge drop in economy at higher speeds.
 

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Re: Speed vs mileage

KiwiPrius said:
I meant to add to the last post that there was an economy run here a few months ago and the first and second place went to Prii, the winner did 4.04 l/100 km (70 mpg!!) all at legal highway speeds, with driver and passenger.
You beaut!! :D
Except that British gallons are larger than U.S. gallons. Your U.S. mpg would be about 59, I believe.
 

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Roger V said:
I have also been passed by many a Prius! Hey, folks, I bought mine for economy of operation, and if slowing down a little can produce these kinds of results, I'm willing!
Heh.. In NJ, where the speed limit is 65, you usually have to do at least 70 to keep up with traffic in the slow lane. I usually cruise home from work in the 75-80 range (middle lanes) and one day I had a Prius just blow my doors off. Funny thing was, it had a vanity license plate about low emissions.
 

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[quote="Jonnycat26]
Heh.. In NJ, where the speed limit is 65, you usually have to do at least 70 to keep up with traffic in the slow lane. I usually cruise home from work in the 75-80 range (middle lanes) and one day I had a Prius just blow my doors off. Funny thing was, it had a vanity license plate about low emissions.[/quote]

You had me worried for a minute, jonny! :shock: But my NJ tag isn't about low emissions. ;) Whew! Wasn't me. :D

Actually, I'm one of those "menace" drivers who keeps at the speed limit or slightly above. Yes, I used to drive 74 on the interstate (speed limit 65) in my old car, but now I get too much fun watching my gas mileage go up. :) Who would have imagined it? :D
 

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Sanny said:
You had me worried for a minute, jonny! :shock: But my NJ tag isn't about low emissions. ;) Whew! Wasn't me. :D

Actually, I'm one of those "menace" drivers who keeps at the speed limit or slightly above. Yes, I used to drive 74 on the interstate (speed limit 65) in my old car, but now I get too much fun watching my gas mileage go up. :) Who would have imagined it? :D
You're down in south jersey? Up here, it's mostly parkway and 287 driving, which is similar to urban combat in some cases. :)

I remember this one particular time on my way into work , I was about a mile from the toll plaza. I called work to say I was running late, but I was nearly at the union toll plaza... maybe about a quarter mile away.

A half hour later I called to tell them I was at the plaza.

It is that bad. :)
 

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Sanny said:
Actually, I'm one of those "menace" drivers who keeps at the speed limit or slightly above. Yes, I used to drive 74 on the interstate (speed limit 65) in my old car, but now I get too much fun watching my gas mileage go up. :) Who would have imagined it? :D
With my old car, I had the mind set that nobody can be going faster than me. I had to pass EVERYONE! I generally drove about 85 MPH. Yes, I was an idiot! But now I cruise nice and slow and smile as everyone passes me. Why? I'm not smiling at being passed but smiling about the great millage I"m getting! :) I normally drive about 60 MPH. I've even noticed a differance between ~60MPH and ~57MPH.
 

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An04Prius said:
Test I did: Same exact trip, 3 times, in almost exact same weather conditions. Only variable was speed. 100% freeway trip.

Cruise set at 75 or 80 38mpg

Cruise set at 65 52mpg

Cruise set at 55 61mpg
I just drove mine 3800 miles from CA to MO and back on I40 & I44. I went 3 to 4 mph over 70 & 75 mph zones...I got 44.0 mpg on the 3800 mile trip. The car performed perfectly.

Only complaint would be that the dealer that changed oil prior to the trip didn't reset the "maintenace" dash light and it came on about 2/3 of the way. I hit the find dealership on the GPS, and wallah!, 2.8 miles away was a deler in OKC that reset the light and off I went.

A truly fantastic car. Oh, I did hit 102mph for a second, oops.....
 
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