CarriageTownJeep

Absolutely, yes, verified. I had the 4.10s installed, saw them with my own eyes before the install. He definitely changed the gear ratio (shows in Superchips).

Tire pressure (just checked) 38psi

CarriageTownJeep

Yes, absolutely (posted that in the long post with all the data).

jchappies

what are your RPM's at 60mph?

CarriageTownJeep

In fifth gear, 2700. I believe about 2200 in sixth, but I'm not going back out (literally just went out to find this out).

Alright, 6th gear, ~2100 at 60MPH, ~2400 at 70 MPH.

Mlupacchino

The JK Jeep Wrangler is capable of getting much better gas mileage than people give it credit for. The caveat being people have to learn how to drive without a lead foot. People aren't used to cruising 57 MPH on the highway, even though it will give them 25% better gas mileage, and they difference in time to destination is negligible.
Note all notes below are in regards to the automatic transmissions.

The first jeep wrangler I bought was a 2008 Rubicon with the old 3.8 mini van engine with the 4.10 gears. When I drove normnal highway speeds (75 mph) I would get ~ 19 MPG highway. Through experimentation, I tested out different speed intervals and found between 55 - 60 mph to be the sweet spot. ~ 56-57 MPH specifically (55 MPH is actually the speed limit for a lot of roads here, though no one obeys it). I was shocked to discover that I would get 5 mpg better on the highway cruising at ~ 56/57 mph than 75 mph, for around 24 mpg highway. Verified through dash computer and gas receipt math.

When I got the 2012 Pentastar rubi and the 3.73 gears, I found that gas mileage was around the same, if not slightly less. I issued a complaint to one of the guys I know at corporate, and I am not sure if it made a difference, but my current 2013 3.73 geared Pentastar Rubi is incredible on gas!

If you coast with cruise control at 57 MPH, I can get over 26 MPH highway and over 500 miles per tank of gas!!

The key being that most people don't have the patience or discipline to coast with cruise control at 57 MPH because it feels so much slower at first, until you get used to it. However, you will find that even over long highway trips, the difference in time between both speeds is negligible, but one allows you over 6 MPG savings!

rob_engineer

So how about us that don't have commutes on highway? Here in NJ, it is actually dangerous to drive that slow on the highway.
Back around 10yrs ago when gas prices peaked I had a class a RV. I read a very detailed and scientific analysis from Caterpillar I think. It was about fuel economy on highway for big rigs with poor aerodynamics. The conclusion was just as you state. The drop in fuel economy goes up exponentially with speed. I think I remember that 55mph was their recommendation for the best economy.

Mlupacchino

That's right, 55 mph is optimum. I say 56 - 57 is better because I've found that with hills, and such, the gear ratio on the autos works better being fixed at that speed than 55, and having overdrive kick in if you have a bit of a incline.

Most highways have speed limits of 65 MPH. 65 MPH is the LIMIT, and you can go slower than that. If the speed limit is 55, like many of the roads here, you should be able to cruise in the middle lane fine. For higher speed highways, I would stick to cruising in the right most lane, or second lane to the right if there are four lanes. Shouldn't be dangerous to do so. Most people just refuse to try it because it is ingrained in them that it is so much slower, and it feels much slower but it really isn't.

A side benefit if that you have much more reaction time if you have to stop / avoid an accident, etc.

Erok

In Texas, most of the highways are 70-75 MPH limits, and our toll roads reach 80!! Even in the right lane, you will find yourself in trouble sometimes trying to go 55. I have chosen 65 as my optimum, but unfortunately with a 4 door, on 35" tires and a 2.5" lift with a roof rack... I still only get 14 MPG

But I bought the Jeep for its Smiles per Gallon and that's working out fine.

bbolander

I typically get 17-18 mpg avg on the highway with some hills. A few times I've gotten 20 mpg on mostly flat highways. Speed is typically 70-75 mph. I consistently use cruise control.

I've adjusted the tire size with my Trail Dash 2 to 33.5" for my 34" tires and it matches the gps.

Mine is a 4 door with automatic. I can see a 2 door with manual getting a little over 20 mpg occasionally depending on the flatness of the trip.