How to get better gas mileage from your Jeep Wrangler TJ

Nashorn101 said:
Ok thank you!

But I always thought that gear ratio had a huge impact on fuel efficiency?
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It might if you were changing to something drastic, but 3.73 to 4.10 isn't going to be that drastic. I went from 4.10 to 4.88 and didn't notice any change in my fuel economy at all. Just more power off the line and less "hunting" for gears.
 
Tristan said:
Life is too short to worry about gas mileage.
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Not for me, round trip to work is 150 miles, 14 times a month. That is why I have a Honda Fit, 35 ave, and has 316000 and runnin like a champ. Been driving my Silverado as of late cuz one of our cars was rear ended and in the shop. 18 on the hwy sucks ass. Thankfully gas is 2.19 at the moment.

Gearing does affect mileage, could be good or bad. Putting your foot to the floor at take off is what eats fuel. Lower gearing can help alleviate that which could improve mileage. Or the gearing could have your rpm's on the hwy in a range where you burn more fuel meaning less mpg. Trade offs, always.
 
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Nashorn101 said:
Well then exactly my point! :p


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Either way though, there was no noticeable loss in mpg from changing gear ratios. Any loss in mpg was so negligible that the only way you would notice is if you were meticulously tracking your mpg (in which case you own the wrong vehicle to begin with :D).
 
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When I stay at 1900 rpm's my MPG's are great. However, I tried the above 2000 rpm's on a 100 mile drive the other day and my MPG's were the same as if I was driving around the city. I guess our gearing and tire sizes are different?
 
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I agree... for gas mileage under 2000rpm rules. With 33s I wish for 3.73s unfortunately my TJR has 4.10s. My old YJ with 33s and 3.07s got 25mpg on the Interstate. Gonna be lots of hate coming soon from the 4.88/5.13 crawlers.

But yes, gear for sub 2Krpm cruise if mileage matters.

The hottest cars in the world today get their top speed down 2 or 3 gears. Audis A8 hits 150mph in 5t gear. The other 3 gears just lower the rpm for EPA and corporate mileage compliance.
 
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billiebob said:
I agree... for gas mileage under 2000rpm rules. With 33s I wish for 3.73s unfortunately my TJR has 4.10s. My old YJ with 33s and 3.07s got 25mpg on the Interstate. Gonna be lots of hate coming soon from the 4.88/5.13 crawlers.

But yes, gear for sub 2Krpm cruise if mileage matters.

The hottest cars in the world today get their top speed down 2 or 3 gears. Audis A8 hits 150mph in 5t gear. The other 3 gears just lower the rpm for EPA and corporate mileage compliance.
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See...that's what I always thought was the key to fuel efficiency! Thanks.

Gosh dang haha that's good mileage for a Jeep!


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Nashorn101 said:
And a sweet looking car too at that. Except, not as sweet as a TJ of course.

Also, is it true that generally the higher speed you are going the more fuel efficient you will be?

I'm trying to figure out in my head what is more fuel efficient: 4:10 gears or 3:73? And which is more fuel efficient at higher speeds?


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Wouldn't that just depend on tire size?
 
Nashorn101 said:
I'd imagine that engine size, gear ratio, and tire size all have considerable influence over MPG.


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True, but outside of engine size isn't bigger gear= bigger tire for better mileage?
 
Forty said:
True, but outside of engine size isn't bigger gear= bigger tire for better mileage?
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A lot of this has to deal with engine efficiency. Bigger tires equals lower rpm. Lower RPM means there are less piston cycles occurring, thus requiring less fuel over time (since more cycles equate to more fuel consumption). However; lower RPM also means low power and torque, and you have to provide MORE fuel per piston cycle to overcome this reduction in torque and power. As a result, lower RPM does not always equate to less fuel consumed. So moderately reducing rpms through bigger tires or different gears can mean slightly better gas mileage, but once you fall out of the sweet spot of the engine's power and torque efficiencies there are no fuel savings to be had. In fact your gas mileage might get worse. One last thought regarding your question, bigger tires are also heavier and more weight requires more fuel to push that weight.

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Yup, lower RPM's do the trick, IF the engine isn't straining to push your rig at those lower RPMs. It's the reason that the four angry squirrels don't produce the gas mileage that you would expect. It's also the reason that the 454 in the Suburban will produce 16 mpg on the highway loaded or empty if you drive in a reasonable manner. Loaded down to max GVW it will produce better mileage than the 350's will. The six banger TJ is the same way. More torque down low.
 
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Head Lice said:
'02 Dodge/Cummins 2500 4x4 ...... 5sp. & 3.54 LS diffs. ...... 6,522 lbs. un-loaded/full fuel tank ..... gets better mileage than the '04 TJ
Burns cheaper fuel too .....
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I'm not surprised. That Cummins engine is more efficient than the 4.0 for sure.

I toyed heavily with the idea of putting a Cummins 4BT in my Wrangler. However, after doing all the research I decided it was just way too loud for me. Since I'm driving around without a top or doors a lot of the time, I don't want that loud diesel sound (and the old diesels are always even louder) driving me crazy.
 
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