Vic R

Disclaimer: I know its not a Honda and I'm NOT buying a JK for MPG, but hypothetically speaking...

I am wondering what is the best match of gearing and tranny for MPG. I had assumed the 6 speed and 3.21, but I see that the EPA has the manual tranny at 15 and 18, while the auto is at 16 and 18. I'm wondering if the 6 speed and 3.21 combo is a little high (low numerically) to get it moving around town? Is there anything published on the final drive ratios of the two trannys - I'm assuming them to be about the same.

I've pretty much already made up my mind on transmission and gearing, but this is just for the sake of discussion...

-Vic

REL1203

best mpg is a Manual tranny 07 without Tow package to get the 3.2 gears.

Duke

for best milage nothing makes an impact as much as.........
smooth light acceleration
don't ever go over 60-65 mph

HULKGREEN

FROM ALL THE POSTS I'VE READ ABOUT THIS SUBJECT .....I HAVE TO AGREE WITH REL1203..................

Are you sure about the EPA ratings?????????

My Window sticker said Manual tranny 17 city 19 highway EPA rating and my 06 Rubicon 6-speed reads 15 city 19 highway!!!!!!!!!!!!

JUSTIN01

The EPA has recently revised there tests. All manufactures in '08 are going to show smaller nnumbers. Tests were done at higher speeds, with a brisker acceleration, and the A/C on.

I don't agree with the gears thing that much. Like Duke said, it's all about driving habits.

REL1203

The gear thing plays a huge part. Diff between 3.2 and the 4.1 is around 15% if not more. Thats means if your doing 2500 RPM with the 4.1, you would be doing 2000-2100 RPM with lesser gears... That can add up a few Miles over a long tank... Its all about the math

Bockwinkle

I have '07 manual 2dr with 3.21 gears and the 17" wheels/tire combo and since I've owned it the average mpg displayed on the dashboard is 21.6 mpg. It is a softtop but the top has been down since I have owned it.

70 mph on the highway in 6th gear is only about 2000rpm.

MJS_Jeep_888

You're correct, BUT as far as Auto trannies go, you'd actually be better off with the higher ratio because of where in the rev range you end up at highway cruising speeds. This engine is optimally efficient, fuel-wise, in the 2100-2300 range (or very nearly so). So, if you're holding less RPM's in 4th with an auto and lower gearing at cruising speeds, you're actually working the engine in a less-efficient range.

RubiconJohn

The information the original poster is requesting is the Break Specific Fuel Consumption (BSFC) graph. This graph always looks like a horse shoe. Which proves you are correct in stating lower RPM's don't always equal better MPG. I would agree 2100-2300 is probably pretty ideal for the JK's v-6.

FRDesign

Identical to my Moms Jeep then.

If my Dad drives it he can get 22-23 MPG. He doesn't use brakes lol, its all about the clutch.