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Discussion Starter #1
So hoping someone has knowledge of this. I usually drive about 55mph. In 4th that's about 2,200 rpm and in 5th that's about 1,800 rpm.
Anyone know which is better for jeep and offers better mpg? Any advice appreciated.
 

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as long as its not lugging the engine down and you still have power then the less rpm's you turn the less gas the engine is pulling in
 

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Sounds to me like your RPMs are too low which will lug the engine which can hurt mpg as much as RPMs that are too high. Cars with their small tires can get away with low RPMs like that but Jeeps with the aerodynamics of a barn door and bigger tires need higher RPMs to run right.

What size tire and what is your axle ratio?
 

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Jerry Bransford said:
Sounds to me like your RPMs are too low which will lug the engine which can hurt mpg as much as RPMs that are too high. What size tire and what is your axle ratio?
These are important questions. Also: terrain and load play a large part.
 

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Discussion Starter #5
Jerry Bransford said:
Sounds to me like your RPMs are too low which will lug the engine which can hurt mpg as much as RPMs that are too high. Cars with their small tires can get away with low RPMs like that but Jeeps with the aerodynamics of a barn door and bigger tires need higher RPMs to run right.

What size tire and what is your axle ratio?
3.73 rear. 31" tire. 99% highway driving. My jeep is all stock.
So I should stay with 5th?
 

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you should stay in 5th,but don't lug the engine,like on a long uphill.Hey Jerry,I seem to remember you posting that you never get over 2000 rpm? Has that changed?
 

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in2jeep said:
you should stay in 5th,but don't lug the engine,like on a long uphill.Hey Jerry,I seem to remember you posting that you never get over 2000 rpm? Has that changed?
Iirc Jerry is almost always over 2k rpm especially on the highway since he has the correct gears for his tire size. At 65mph I'm at 2500rpm myself.
 

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Hey Jerry,I seem to remember you posting that you never get over 2000 rpm? Has that changed?
At 65 mph, it's turning around 2100 which is just way too low with its 35" tires, 35" tires, and 42RLE transmission. To me, it's lugging at 65 so I spend half the time with the overdrive shut off. I'd like to have a 5.13 which would give me another 150 rpms but even that's not really enough... 5.38 would be ideal but 5.13 is as low as you can put into a Rubicon D44.

3.73 rear. 31" tire. 99% highway driving. My jeep is all stock.
So I should stay with 5th?
At 55 I'd probably be using 4th gear a lot, the engine just seems to lug at anything close to or under 2000 rpms.
 

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In my 06 i have 3.73s for the moment(aint regearing till tax time w/ lockers) and im running 36's. I dont use 6th, just keep it in 5th on the highway...RPMS stay about 2100 and cruise holds that speed even on hills. Not bad mileage...220 or so a tank. Would be better but im weighted down with bumpers/tire carrier/winch etc. Its not ideal by no means but gets me by till tax time. Sadly get better mileage then my buddy with a bone stock 06 rubicon lol.
 
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