I just bought an 07 black laramie with 13k miles...thing is immaculate and I love it. Im far from being new to big engines and fast cars, but something's not right here.

I just picked it up on saturday and im averaging 8-9 mpg on the overhead console thing. I am a lil harder on the gas that normal driving but nothing drastic. Even cruising to work at 75mph, i was gettin 9 mpg. Truck is a 4dr laramie with a tonneau cover and mopar dual exhaust and the 3.93 rear.

I thought it just might be the electronics messed up so I CALCULATED IT MANUALLY based on the half tank that I used up and my average MPG were 9.1. If I drive super conservatively on the highway at 65mph, the best the overhead will show is 14.4mpg. Im hearing of guys on the net gettin 20-22mpg highway.

9-10mpg would be fine if I was blasting the throttle off of every light, but Im driving conservatively and getting that amount.

Is this normal?? I understand its a big engine and a big truck, but 8mpg highway is dissapointing...i was expecting atleast 14 highway.

That MDS doesnt seem to be doing anything.

Any ideas would be greatly appreciated and I look forward to talking to you guys in the future...

 

did u reset it on the overhead?

 

Haven't had a lot of testing but my dads 07 hemi all stock is getting about 11-13 around town and 16-18 highway

 

Yeah, you got some kind of issue going on. Most 06+ MDS Hemi owners report about 14 mpg city and somewhere around 20 on the highway.
Hell, I have an 04 without MDS, have a lift and 35" tires, weigh in at close to 7000 lbs, and still manage to get 11 mpg city and 16 on the interstate...

 

well thank you all for the prompt responses. YEs I reset the overhead, but what difference does it make? Like I said before, I confirmed the accuracy of the overhead when I filled up my tank again. Im averaging 9mpg.

Now that we can agree theres a problem, when I take it to teh dealer tomorrow or monday, they said they're gonna put it on the computer diagnostic. As it is the service guy is giving me, "ohh well ya know it is a big powerful engine and that is a big heavy truck, so gas mileage is gonna be difficult" Of course, I told him I didnt care if it had a rocket engine in it, my complaint isnt the 8mpg per se, but the fact that no one else with that same big engine and heavy truck are getting this mileage.

I have a feeling the diagnostic wont show anything. Hopefully it will, but I just doubt it. How do I argue this when they say, ohh, well theres no "codes" so everythign is running fine. ??

 

also, any idea on what the cause might be??

Like I said, truck has only 13,000 miles on it and previous owner babied the thing. I have the dual exhaust, but if anything I would think that would help the mileage. I have a tonneau cover, but i cant see it losing me 5 mpg.

I really need your help guys! I love this truck but its gonna eat away at me if I feel like something's not right with it.

 

New plugs?
New air filter?
Fresh engine and transmission oils?
I even had my 03 Hemi battery going out which caused a 1-2 mpg decrease in the mileage I was getting, due to the extra load on the alternator.
Could be a lot of things.
Also, I'd do a "cold" PCM reset.
Then drive the truck easily until it learns your driving style.
Hope this helps?
Al.

 

First things first. Don't run 87octane. You need to run at least 89octane or you will possibly damage your pistons from detonation. If you are using 87oct, then i can see why you would be getting bad mileage.
I have my MDS turned off, my shift points raised and a few other tweaks that actually have gained me mileage. i can really lay into it all around the city and still manage to get 13-14mpg's. Highway is around 15/16. I usually get just a little over 300 miles for 22gallons. (310ish)

 

I agree, reset the PCM then see how it goes. It could be all kinds of things causing poor mileage. I know if I do short drives (to the carpool lot) with it being cold out, I only get 11-13... and I've got a few mods done. I still get 15-17 on the highway with 4.56 gears at 75mph.

another thing you might consider is what speeds/RPM's your driving at. My truck is really picky when it comes to this. I get better mileage at 75MPH than I do at 70MPH, because my power band changed when I installed my x-pipe. It seems like everything I change, changes my peak fuel economy/RPM range. Just my $.02

 

Thanks again for the responses. ALl fluids are like new. Truck only has 13k on it which is why I'm inclined to rule out plugs, and wear/maintenance items of that sort. On highway, I cruise around 2000 rpms at 70.

How do I do a "cold" reset? unhook battery?
IF I do have the comp relearn my driving, shouldnt I drive it a lil aggressively, so it compensates?? I would think if it learns grandpa type driving, then any somewhat agressive driving would really throw it off???

If I do a "cold" reset, will it erase any possible "codes" im having when I bring it to teh dealer?

Thanks again, you guys are really helpful.

BTW, Im running Shell V power high octane.