That's the trouble with these anecdotal reports: They mean very little without scientific rigor applied. I removed my MBRP-equipped hardtop and tools and experienced approximately a 1 MPG improvement in gas mileage. But how many folks keep track and admit they bought gas at a different place, removed unnecessary gear, had different weather, etc? MPG numbers quoted on this forum are extremely unreliable ... including the one I just quoted!!!

 

The reason I would say that this takes into account ethanol gas is that around here in PA where I usually get 22 - 23 mpg on the highway most stations I fill up at say "contains 10 percent ethanol". Also it would be awful coincidental that after filling up for 3 months at all types of different stations (Exxon, Conoco, Kroger, HEB, Fast Track, etc.) and getting 18.5 - 19.5 mpg like clockwork, that as soon as I got to a place where the ambient temperature got below 90 the fuel economy that I started getting the same fuel economy I see in PA.

 

So... Computer was showing 18.4, and my manual check was 17.85. Hmmm...

 

Speed is the difference maker for me. I've done a few State College trips and if I try to keep it at 70 I'll use over a tank. Two weeks ago I kept in right around 60 and made it with over 1/4 tank left.

I did Jacksonville, FL to State College and kept at 60 the whole time, my numbers worked out to just over 25mpg.

 

I track my milage in a spreadsheet. I document where I fill up, when I fill up, any weather conditions, driving style, mods done to Jeep, etc. So I know EXACTLY what helps and what hurts.

I was pulling a consistent 17 MPGs in July in very HOT weather all month. So far, August has been cooler and I'm seeing a solid 18 MPGs. This is with everything else constant.

Is it just the cooler weather? Or the fact that the A/C stays on less? I don't know, but below-90 weather DOES = better mileage for sure.

 

It's been much cooler here in Western KY as well. The only time I run the AC is when the kiddos are with me. Other than that.. I don't care if its 100, I still have at least the windows down. I do notice a difference in MPG when I'm running the AC, but since I don't use it that much, I have to assume it's the cooler temp outside.

That 17.8 that I'm getting is me babying the pedal. This is on a Unlimited auto with 3.73. If I drove it like I do my wife's Commander, I'd prolly only get 15 or 16. Most of my driving is short commutes. 15 miles to work with hills and cut through one small town.

 

I've noticed over the last several years that my mileage peaks in the moderate temps of spring and fall, with usually an extra 1-2 mpg. This was the case in my WJ as well as my JK. I have also noticed altitude does play a part, though not as much as temps seem to (at least in my JK).

Another part of this, I've noticed the mileage readout from the trip computer is regularly about 2-3mpg off in my Jeep. I have been tracking all of my fuel and maintenance with an iPhone app since I got my JK 2 years ago, and it makes a big difference being able to have the backlog of data. I used to keep a log in my old XJ on a notebook, but found I got lazy way too often.

 

I just plan on paying $75 per fill up. Anything less is just a little bonus. There are just too many variables when it comes to fuel economy.

Instead, focus on finding a gas station that has the lowest costs, reduce your weight by not carrying all your gear when its not needed, and obey the speed limit.

 

the biggest mpg robber by far is my a/c... followed by a strong head wind! I drop a couple of mpgs on the same commute with a/c on. Since the idea behind "cold air intakes" is to seek cooler air it can't help with the temp drops into the 70s or lower.