bOLsAK=3

OK. Here it is(Sorry it took a bit), my total update from the thread I originally posted about trying to get better gas mileage out of my JK.

First I'll start off by explaining that my goal was to find a way to get a full 300 miles out of a tank of gas before the light came on. I planned to do so by finding a way to do it with only minor modifications and with using the least amount of moola that I could.

I own a '07 JK Sahara 2 door with an automatic, OE 18"s with OE bridgestones(tires at 36psi), 4.10 axles, soft top, no lift(yet). Mods are below.

I live in an urdan area of south Florida where the only hills are bridges. The highway limits are 70mph and the local limits are 40mph. The weather has been in the 90's during the days, and mostly the 80's at night with %100 humidity for %99 of the time since I started this. Up until the last three days, that is. It has rained every day this summer in the afternoons so the top has been on for the most part.

My driving habits are somewhat typical for this area, I believe. I like to do 75mph on the highway, sometimes hitting 80mph. 35-50 around town from light to light.

The averages I have posted below are simply that, averages for my driving conditions.

My method of calculation was to fuel with Mobile gas stations only, fill it to the very rim at every fill (And I mean to the rim), and then divide the mileage by the number of miles traveled.

The modifications that I decided to go with were rather simple and are just add-ons because I didn't want to take away from the factory warranty or the overall reliability. Nor did I want to take away from the performance. In fact, I wanted to add performance AND save fuel. The mods include an Airaid intake, a Jet stage1 performance module, Greased Lightning Teflon additive, and adjusting my fuel octane. I would have really loved to have gotten a cat-back for this, but just haven't decided on what I'm getting just yet.

I am posting the results as followed: Fuel-Chip-Intake-Additive. The reason why is because I researched my mileage in that order. First I played with fuels, then I added a chip and played with fuels, then I added the intake and played with fuels+chip, and finally I added the additive.

results are as followed:

Fuel:

87= 14-15mpg
89= 17-18.5mpg
93= 15.5-16.5mpg

Fuel+chip:

87= 13.5-15mpg
89= 16-17.5mpg
93= 15.5-16.5mpg

Fuel+chip+intake:

87= 15mpg
89= 17-18mpg
93= 16-17mpg

Fuel+chip+intake+additive:

87= ? (haven't bothered)
89= 18.5-19.5
93= ? (haven't bothered and why should I when all other attempts have had similar results?!)

My take:

I was absolutely surprised at the mileage gains with both the additive (Greased Lightning) and the mid-grade octane fuel (my two highest gains). I surely thought that the intake would have given me the biggest gain of all, but I only saw a .5-1.5mpg gain on average out of it. The fact that the only add-on that I lost mileage with was the Jet surprised me too. The jet gave me a an average loss of .5mpg across the board. But did add a small amount of power.

With each of these mods I noticed a seemingly equal amount of power added with each one. I would surely recommend any, if not all, of these for anyone trying to get more bang for your buck. My Jeep has a much more smooth and tolerable amount of power now, and with better mileage to boot.

I am now averaging a full 18-19.5mpg

I must add to all this that I found my best mileage (according to the computer) was when I was traveling between 40-50mph. According to the computer (and don't let this confuse you since I don't rely on the computer for calculations) I get 27-ish now with all the mods, without stopping and going down a long highway. In other words, cruising between 40-50 for longer distances is where I saw my highest fuel savings(according to the computer). On the flip side, The quickest drop in mileage came from 65-80mph and when leaving a stop light. I do like to look down at my fuel average computer and even though I understand that it is not perfect, it has been within 1-2 mpg of my calculations if I restart it when I fill and then look at the final average of the computer in comparison to my calculations.

Again this is info that I have gathered pertaining to my own experiences. These are all averages and in no way a perfect science. I'm not here to push any product. Just a simple experiment and how it was done.

And yes, I finally got 300 miles out of a tank.... Once so far.

USAF_GroundRat

Great write up... you get the JK Scientist Of The Year award for this one!

bcperry2000

so which do you recommend most? for both performance and mpg?

ALSO, did you reset you ECU after each mod? wouldn't that make a difference?

RedRockJK

VERY interesting. I would suspect that the Mobile stations in your area have more alcohol in the 87 Octane gas than the 89. I found that happens at some stations in my area. After I realized I would get worse gas mileage using 87 Octane from certain stations, I avoid them now.

One thing that would be very interesting is if you tried 87 Octane from a few different brands in your area and check the results. I've had very good luck with 87 Octane at the Murphy stations here (Wal-Mart), and also Shell and BP.
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bOLsAK=3

I had to disconnect the battery after the intake, and after the chip. That is it. As for which do I recommend for both mileage and performance........ Gotta think about that one ...... I know it sounds retarded, but adding the Greased Lighting gave me better results than I hoped for really. But I really, really love my Airaid. The combo of the two is what I would go with because the Greased Lightning was only $12 and the Airaid just rocks.

John L

Open up the exhaust and you should see more gains.
Engine=big ass air pump.
More air in (intake)+more air out (high flow muffler)=more efficient air pump.
The louder things get, the more efficiant they are.

bOLsAK=3

I'm just waiting for a complete back to front kit. Headers, cats, and exhaust. At least I'd like to. But according to my budget, I'll probably end up with a cat-back instead.... Eventually.

MJS_Jeep_888

First, I appreciate you taking the time to post these results for us all.

I need to point out that (among driving style, etc., and lesser variables) there's a BIG glaring variable in your test: mileage on the engine. I found that my BEST sustained miles per tankful didn't come until after 8000 miles, and my trending (I use a spreadsheet) shows a near-continuous improvement in MPG as my engine is further "seasoned"...

How many miles were on the clock when you started your testing, and how many were on the odometer at test's end?

Again, thanks!

bcperry2000

i've heard this several times and i am praying that its true. my mileage absolutely sucks. i'm about 150 miles on this tank and the light should come on in about 30 more miles :(

Major Ho

Two friends and I, also with jeeps, a TJ and a WJ decided we would have a fuel suck off competition. See who could get the best mileage since we all have our handicaps between mods or predisposed with large displacements.
Heres a screen shot of the numbers Ive been keeping track of for my JK.

Heres another adjusted for larger wheel circumference. I determined that for every 10 miles the odometer read 9.15 miles

So Im getting an average of ~14 or 15 depending on how you look at it.

Ignore some of the other stats, its just for our own entertainment