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 Post subject: Most efficient driving speed?
PostPosted: Tue Jan 10, 2006 1:37 pm 
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'Just curious whether any of you out there have 'experimented' a little with your driving speeds (mainly talking out-of-town/highway here) to see which speed gives you the best mileage? Most sources I've seen talk about ideal efficiency being reached at between 40 and 60mph, with efficiency dropping off pretty significantly over 60mph:

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

Mine seems to be best (to the extent that mileage computer can be trusted) in the high 50s/low60s.

I've decided my best solution is to find a way to be constantly driving DOWNHILL :)

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PostPosted: Wed Jan 11, 2006 11:16 am 
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I drive 70 miles a day toa nd from work....67 of those miles are on the higway. Before I got my lift it seems to me that about 65 mph had the RPM's right at or just below 2000. That seemed to be my best milage. And after the lift it tends to be that same. Except now when my RPMs are at 2000 i'm actually going about 71-72 mph.

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PostPosted: Thu Jan 12, 2006 10:54 am 
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IMO, between 50 and 60 mph unless you're driving a CRD Libby, in which case I'd say between ~58 and 65 mph.

You want to go just slightly faster than the slowest speed that you can engage your highest gear and not "lug" the engine. My auto tranny locks up at about 45 mph, so I'd say that 50 mph is probably pretty close to ideal with the stock tires (but I can't stand to go THAT slow on long trips, so I do ~60). If you're running oversize tires (lower RPM's for the same speed), you might need to go a little faster (than 50) to achieve your best mileage.

Luis

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PostPosted: Thu Jan 12, 2006 12:41 pm 
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65 mph nets me 17 mpg with 255/70's and a rusty's lift

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 Post subject:
PostPosted: Thu Feb 02, 2006 12:24 pm 
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66 MPH is my best time/fuel effeciency... 23+MPG

45MPH nets me about 27MPG...Yes I do drive this slow on day to day trips under 25 miles one way. Ain't hardly no time diff.


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PostPosted: Sat Feb 18, 2006 5:41 am 
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just took a 170 mile trip home, 20 of which at the end of the trip were stop and go behind a school bus (i hate public transportation)....i just got the libby in january, but when i took the trip down to school i went anywhere from 78-85, lets say about 82 avg....i got 16.8mpg. I took the trip back the other day, went 70, got 22.1 mpg. 20 of those were horrible city driving conditions (constant acceleration and stop/go with almost no cruising). i'm betting i coulda got about 22.5 without those lousy 20 miles

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 Post subject:
PostPosted: Mon Mar 20, 2006 5:42 pm 
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Ive gotten 23-24mpg doing 40-45 before. Up around 60-65 I get 21-22mpg. If Im going under 40mph Ill turn o/d off and lock the torque and I get around 23mpg.

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 Post subject:
PostPosted: Mon Apr 10, 2006 4:59 am 
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I drive fairly aggressively at get about 17.5 in mostly suburban driving. This seems to be a bit higher than average for non-freeway driving. The 6spd is the difference, i guess?

My only tank of at least 75% freeway netted me 21 mpg, but I was humping it pretty well (80-85).

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 Post subject:
PostPosted: Sat Jun 10, 2006 8:17 pm 
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Believe it or not I've notice I get similar mileage at 83mph as I do at 58, 23 or 24mpg. I drive from AZ to OH a couple of times a year and when I do I ONLY stop for gas so that’s from top of tank till empty.

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PostPosted: Sat Jun 10, 2006 9:27 pm 
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I've driven from Phoenix to Albuquerque many times in my Sport, and with the cruise set at 75 on the freeway I can average 22mpg. Best yet was about 23.5, but I was driving in rain on that one and had slowed to about 50 along a lot of the route; I hate driving at speeds too fast for the road conditions.

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 Post subject:
PostPosted: Sat Dec 16, 2006 12:47 am 
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mine locks the torque converter in O/D at 61mph, unlocks it at 59, if exceed 61 then set cruise for 60, the computer says a steady 27-28 mpg on level hiway. @1900rpm

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 Post subject:
PostPosted: Thu Mar 29, 2007 5:49 am 
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My driving conditions vary due to wind and hills, but I seem to always get at least 20 mpg running between 65 - 70 mph. I would say that 1800 - 2000 RPM’s provides the best mileage gains. I’ve actually recorded 20 mpg at speeds as high as 75 mph. The best mileage recorded is 22 mpg running 70 mph. My Jeep is all factory beside the shift kit, but I hope to squeeze a few more mpg somehow. My first upgrade will be a aeroturbine muffler. I’m pretty sure this will provide at least a one mile per gallon increase.

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 Post subject:
PostPosted: Wed May 09, 2007 5:05 pm 
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With my 5-speed in 5th gear at 60-62mph (Speed limits on the expressways in NY are still 55mph), cruise control on and RPM's about 2150, I average about 18.5 mpg with my mods (see signature). Next I'll be experimenting with acetone. Mods to come may include the Fitch catalyst and Race Ace louvres.

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 Post subject: 29.4 miles to the gallon
PostPosted: Sun Jun 17, 2007 4:29 am 
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Location: Fairbanks, Alaska
The best mileage I have had thus far is 29.4.
Running several trips between Fairbanks and North Pole Alaska.
Flat 12 mile stretch that is currently in reconditioning. Speed Limit 45. My average speed was 40 with my tire pressure at 40psi. this has been a magic combonation for me. I wonder what will happen when I do a lift and tire combo... :lol:

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 Post subject: Re: Most efficient driving speed?
PostPosted: Sat Mar 06, 2010 8:53 pm 
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I set the cruise at 57-58 around 1750+ RPM and at that I can get in the mid 30's on the highway.

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 Post subject: Re: Most efficient driving speed?
PostPosted: Sat Mar 06, 2010 9:39 pm 
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Way to bring back an old thread :jester:

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 Post subject: Re: Most efficient driving speed?
PostPosted: Tue Mar 23, 2010 10:33 am 
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CRD Joe wrote:
I set the cruise at 57-58 around 1750+ RPM and at that I can get in the mid 30's on the highway.




How are you able to stay at 1750 rpm at 57-58 mph? At 60 mph, locked up in 5th gear, I am turning 1700 rpm. At 59 mph, the tranny downshifts into 4th, and the revs go higher, like over 2000 rpms.

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 Post subject: Re: Most efficient driving speed?
PostPosted: Mon Mar 29, 2010 3:38 pm 
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The last trip i took recently was from Va to Ga and i top my all time record of 36.5 and got 38.5 mpg with my CRD. What I do is Get her in 5th gear locked up and with cruise on i drop my speed back to 58 , 59 at 1625 rpm. she will hold that in cruise on the hills on the highway. I sometimes can go 57mph in 5th gear locked up if it is flat but i dont run on flat for long in Va.

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 Post subject: Re: Most efficient driving speed?
PostPosted: Thu Apr 08, 2010 8:45 pm 
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74 MPH
at 1950 RPMs
and 21.5 MPG
hit the hills though and the 265-75s kill me :-)r
someday he'll finally throw the 4.10s in

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 Post subject: Re: Most efficient driving speed?
PostPosted: Thu Apr 08, 2010 10:10 pm 
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1500rpm
52mph
24mpg

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