I installed my RR XHD bumper, winch hoop, and Smitty XRC8 winch last weekend. I have since noticed something interesting!

After I lifted my Jeep, 4" Superlift w/ 37" tires, my gas mileage went down to a consistent 12mpg on the computer. I know this isn't accurate with the larger tires, but it has allways been high 11s low 12s for the past 6 months. And many times I would reset the mpgs after filling up, and would end up with the same figure by the end of a tank.

So when I installed my winch, I had to disconnect the battery. Afterward, the Jeep seemed to drive and shift just a little better (possible ECU reset?). I figured it was just in my head, but last night I looked at my mpgs and it is registering 14.9 after a half tank of gas!

I haven't been driving it any different, so I'm wondering if something with the bumper/winch made a difference. Now, it is still kind of soon to know for sure, so maybe it will drop, but we'll see.

Here are some of my thoughts as to why it may have gone up:

1. I don't think it is a weight issue, because the RR bumper alone felt heavier than stock. then add the winch!

2. Coudl the extra weight on the front have dropped the front, increased the rake, and made the airflow over my Jeep just a little better?

3. As for airflow, the bumper is a stubby, so could the increased airflow in front of the wheels have somethign to do with it?

4. Also, In doing this, I got rid of that big plastic piece hanging underneath. Better airflow, maybe?

5. I had to disconnect the battery, which may have reset the ECU and made it run better, sonce these ECUs "learn". What scares me is that if this is the case, why the hell does it run better after the reset? I may hook up a battery switch and disconnect the battery once a month if it looks like this is the reason.

Or any combination of the above!

I can't wait to see if it holds the MPGs over a couple of tanks!

 

probally got worse you just dont know it

 

Actually, I just had a thought that makes the most sense. I'm pretty sure the winch/bumper combo dropped the front 1/2-3/4 of an inch. That could possibly throw the fuel guage off which the mpg computer is based off.

 

figure out your MPG with out the Jeeps computer. Usually those are only accurate for the last 10 miles driven. Where you have bigger tires though, if you don't have your speedo configured for it then its tough to figure out how many miles you actually gone.

 

That was my thinking your fuel gauge is off alittle throwing you gauge out. Other reasons for better fuel mileage.... How many miles on our motor???....Could be your engine is starting to loosen up alittle and broke in. Have you switched fuel stations of late???


I am not sure if the Jeep is re-learning your driving habits. I know on my Dodge Magnum R/T with the MDS Hemi, once I or the dealership disconnected the battery to complete some work on it, the MDS would have to relearn my driving habits again and that first or second tank I would get horrible mileage and then it would spring back up! Then I found out that some Hemi MDS you had to perform a MDS recalibration 7 steps after a battery disconnect and it actually worked. So, this could be a similar issue with the computer is just recalibrating based on your driving habits.

 

I do check my actual mileage per tank via the odometer. I only use the MPG computer for the heck of it, but I haven't seen it read that high in a long time! Anyway, I'll know in a feww weeks and a few tanks. I ride my motorcycle alot to help out on gas, so it may take me a month just to go through 2 tanks, if that!