RATM

At highway speeds with my soft top off I lose 1mpg. With my soft top off and my doors off I lose about 1.5mpg.

But the ride with the top and doors off is priceless.....

Hell, this is from 6am yesterday morning with the top up, windows up, vent blower on, A/C off, running 70-75mph in 6th with the cruise mostly on. Reset the idiot gauge @ exit 222 on I-75 in Henry County south of ATL, through Downtown and took the photo as I passed exit 7 on I-575 in Cherokee County well north of ATL. 2 door, 3:21 6sp sittin' on the 17" factory bullchit.

Even if the gauge lies so bad I was only getting 20 it's still a whole lot better than the 07 5.4 CC FX4 the Jeep replaced.

JPop

The 1800/2100 rpm sounds like the converter not locking up, usually around 15% more rpm when unlocked. Crosswinds and headwinds can cause serious mpg swings and a tailwind won't buy you much of anything. Soft top, rear windows on can give you a bigger aero footprint when dealing with crosswinds, causing you to counter-steer into the wind while increasing the load to sustain speed.

Perhaps the extra load never allowed the converter to lock up and that was your culprit. On my truck, I'll often need to overshoot my intended speed, backing off so the converter will actually lock up. 1800 rpm would seem to be about the minimum to sustain highway speeds and my guess is that the throttle position sensor never got to a point where the PCM locked up the converter.

Your mpg is also off by the same 15% or so, further lending credence to the converter being unlocked.

0311sgt

i agree with you ;however, no one here YET has complained about MPG. This guy just aksed why it was different between the soft top and bikini top. He didnt whine or complain at all.

JKMARINE

I noticed when I go over 2,000 RPMs the fuel guage drops like a rock and so does the MPG guage. I just can't keep my foot off of that damn skinny pedal though.

JPop

A lot of that will have to do with the speed you are trying to maintain, especially when your jeep is just barely hanging on to make enough power to move you along on the highway flats at a given speed. For instance in my JK, I can maintain 65 mph in 6th gear at around 2,000 rpm. if I try accelerating from there, or I have wind or a hill to encounter mileage, power and efficiency goes out the window. 5th gear and rolling at around 2400 rpm, no mpg differences, more power when I encounter a hill or headwind.

The primary difference is at these lower rpms is that your vehicle is more starved for air more than fuel. Adding more fuel in that situation squashes efficiency and becomes a real mpg killer because twisting at lower rpm doesn't enable enough air intake. This is in part why there are so many who claim mpg and efficiency differences after upgrading to a steeper gear.

JK Rocker

Arizona is a spiritual vortex. Its sucking all your energy, man. Thats where your RPMs went, into the vortex!

KC9BIW

I agree, but why is it I always get the crappy end of the stick when it comes to MPG? LOL

highergr0und

It's probably just due more to wind direction than anything. It should not be quieter with a bikini top than with the soft top unless the wind was up. On my last big drive, I got a little over 20 MPG from MS to MI (soft top up no windows), but on the way back (same config), it was all into the wind and I think I got 16-17. One tank lasted only 200 miles, but I was pushing hard into the wind the whole time. I average about 70-75 on the freeway.

I also never pay attention to the radio volume. That's weird to me. I just checked it and I was on 22 listening to Rick and Bubba on the way to work today with the top down and doors on going to work today.