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What do you guys find is a good crusising speed for fuel economy?

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Discussion Starter #1
I was driving on the 400 today (main highway in southern ontario) and I noticed at 120 km, my rmp is around 2800, at 140 its around 3200-3400. Im wondering roughly what speed you guys find is good for fuel economy on a highway/freeway
 

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I find 130km/h in the Mazda3 is a good combination between speed and fuel economy. Obviously 130 isn't the most efficiant speed though.

When I drive my Elantra, 110-120 is a "good" combo. Its a high revving engine. At 120 I'm spinning about 3300 RPM!!
 

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I think around 120/130
 

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In the city 80 KM/H in 4th and on the highway 120-130 in 5th get about the same milage for both. Lately it has been about 7.5L/100KM, according to the computer at least.
 

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Discussion Starter #5
i have the sedan 2.0 so its a 4 speed. Today while driving: I noticed that 100km/h is just under 2500 rpm, while 110 km/h is just over 2500. 120km/h also seems to be around 2900 while 130km/h is just over 3000.
 

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The slower you go, the better fuel economy you will get. So the question is how slow are you comfortable going? For me...

...going 55 I get about 40-45mpg
...going 65 I get about 35-37mpg
...going 75 I get about 30-32mpg
 

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[quote author=Kyle Hadcock link=topic=71240.msg1261249#msg1261249 date=1173634716]
The slower you go, the better fuel economy you will get. So the question is how slow are you comfortable going? For me...

...going 55 I get about 40-45mpg
...going 65 I get about 35-37mpg
...going 75 I get about 30-32mpg


[/quote]

not really, it depends on where your engine produces good power while not sucking mass quantities of gas
 

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Aerodynamic drag is proportional to the square of velocity. That's why the Prius gets better EPA ratings in the city test (20 mph average) than the highway test (48 mph average). I'd guess that the lowest speed at which the engine runs well in your top gear probably provides the best fuel economy in most cars. So that would be around 60 km/hr (37 mph) in 5th gear (about 1500 rpm). It could be lower though. Most wouldn't consider the gains of going that slow to be worth it anyway.

Patrick Bedard of Car and Driver did a little experiment with this in a Lexus RX400h (February 2006) and achieved the following results at steady speeds:
40mph - 49.3mpg
50mph - 41.0mpg
60mph - 37.2mpg
70mph - 31.7mpg
80mph - 26.1mpg
Bedard's test was a flying start test with no acceleration or braking, so the hybrid system was not a factor. Too bad he didn't do a run at 30 mph; I'd like to know if it does better at even lower speeds.

I just stick to the speed limit - 90 to 110 km/hr - on highway trips, and I've averaged 30 mpg (7.8 L/100km) overall since I bought the car.
 

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[quote author=m3forlife link=topic=71240.msg1261713#msg1261713 date=1173656402]
[quote author=Kyle Hadcock link=topic=71240.msg1261249#msg1261249 date=1173634716]
The slower you go, the better fuel economy you will get. So the question is how slow are you comfortable going? For me...

...going 55 I get about 40-45mpg
...going 65 I get about 35-37mpg
...going 75 I get about 30-32mpg


[/quote]

not really, it depends on where your engine produces good power while not sucking mass quantities of gas
[/quote]

I reiterate, the slower you go, the better gas mileage you'll get. Try it, hehe. If your car has the instantaneous MPG gauge, and you pay attention to it, you'll agree. Granted, I'm not saying put it in 5th gear and go 20 MPH. I'm being realistic and talking about highway driving, like AGM_Ultimatex is asking about. :klavergreg:
 

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i've got 50,000 miles now, and average 29mpg. Best long haul test though, was a 1400 mile trip from Milwaukee to Toronto & back.

Never dropped below 80mph.....cruised along 402/401 at 145 - 155 kph. topped out 170 kph around London. plus some city driving in T.O. (maybe 100 miles of the 1400 total)

29 mpg.

I'm kind of believing that with the high revving 2.3 engine, that the higher speeds don't impact our gas mileage nearly as much as some of the larger engine landboats around. Had a 3.8 litre Windstar and it usually did about 20 l/100 km at 120 kph. but on a few extended runs (Montreal to Ottawa for about 2 hours on 4 different trips) pushing it to 160 kph drove the gas mileage up to 19 l/100 km
 

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[quote author=shenon link=topic=71240.msg1337572#msg1337572 date=1176614135]
i've got 50,000 miles now, and average 29mpg. Best long haul test though, was a 1400 mile trip from Milwaukee to Toronto & back.

Never dropped below 80mph.....cruised along 402/401 at 145 - 155 kph. topped out 170 kph around London. plus some city driving in T.O. (maybe 100 miles of the 1400 total)

29 mpg.

I'm kind of believing that with the high revving 2.3 engine, that the higher speeds don't impact our gas mileage nearly as much as some of the larger engine landboats around. Had a 3.8 litre Windstar and it usually did about 20 l/100 km at 120 kph. but on a few extended runs (Montreal to Ottawa for about 2 hours on 4 different trips) pushing it to 160 kph drove the gas mileage up to 19 l/100 km
[/quote]

29 mpg is amazing. I haven't really attempted to get amazing mileage, but I average between 25-26, quite consistently, on a manual transmission.
 

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I typically cruise on the highway 70-75 mph but when gas went over $3 a gallon again, I decided to cut down on the speed a saw a 15% increase in mileage. I was getting 31 mpg at 70-75 mph but now I keep it a 60-65 mph and i am getting 35 mpg. it takes me 5 minutes longer to get to work, but who is in a hurry to work???
 

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I usually go 80+ however I got speeding ticket the other night and now I go about 70-75
 

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Discussion Starter #14
Speaking of speeding, I was on a bit of a straight stretch, which i consider a landmark of about 60% of my drive home from town, its where the canadian shield starts, and its a nice set of bridges. I'm going moslty 140 the whole way, but around here i started kicking it up, brought it up to around 168 :). I took my foot off the gas as a bend was comin up, as soon as I started to turn, ahead of me was flashing red lights, and in an instant i pressed the break and went down to 120. As I passed the red lights, they pulled over a truck I think. Was a couple of cruisers, and didnt look quite like a speeding pullover, but sure glad I slowed down.
 

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5 minutes at a low hourly rate of 9.00/hr (which most people driving 04+ cars is probably a bare, bare minimum) is $0.75

Gas is 3.30/gallon where I live.

0.75/3.30 = 23%

Or your average gas consumption would have to decrease by 25% to outweigh 5 minutes at a low rate.

"But I work for salary!"

Well, in that case, you know that you're probably going to be working in excess of 40, 50, maybe even 60, hours a week, and thus your free time is even more limited and valuable than the gentleman making $9/hr.

The opportunity cost of time is much more expensive than most people make it out to be.

-edit-
In response to the focus question: My cruising speed is generally about 40-45 city, 80ish highway (MPH)
 

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However, we are also talking about a hybrid.

Scientific testing of vehicles show that an automobiles peak efficiency is in the speed realm of 52-60mph depending on gearing, rolling resistance and coefficient of drag/frontal cross section.

Engines actually are more efficient, breathing wise, at higher RPMs then at lower RPMs. However, you also have a down side of the fact that shorter gears have a greater parasitic loss of power. With the combination of rolling resistance (linear increase with speed) and air resistance (2nd power increase with speed) and short gears being bad to get the motor into a range in which it is really efficient you come up with most traditional gasoline powered vehicles being most efficient in that speed range (it was either EPA or I think actually DOT did a study on it about 8-10 year ago that I was reading. Had nice line graphs etc with their testing results on several vehicles).
-Matt
 

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[quote author=azazel1024 link=topic=71240.msg1459592#msg1459592 date=1180978785]
Engines actually are more efficient, breathing wise, at higher RPMs then at lower RPMs. However, you also have a down side of the fact that shorter gears have a greater parasitic loss of power. With the combination of rolling resistance (linear increase with speed) and air resistance (2nd power increase with speed) and short gears being bad to get the motor into a range in which it is really efficient you come up with most traditional gasoline powered vehicles being most efficient in that speed range (it was either EPA or I think actually DOT did a study on it about 8-10 year ago that I was reading. Had nice line graphs etc with their testing results on several vehicles).
-Matt
[/quote]

I would be fascinated to see an EngineSpeed vs MPG graph of that new Chevy 4/8 cylinder SUV. Without knowing the crossover speed, if I had to guess, I'd say that it would be most efficient (4 cylinders in optimal operating speed) at about 45-50?

Anyone know any more info about it? I know some people that are looking for a larger car to haul stuff around town and short highway trips, without getting shit mileage, for a halfway decent price (ie. no lexus hybrid).
 
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