Poor fuel economy/loss of power

Jmdoft91 · May 10, 2013

I bout my ram 1500 mega cab 4x4 w/ the hemi about 2 months ago and when I purchased the vehicle I noticed it had a K&N cold air on it along with a single in dual out flowmaster muffler as well. So I knew the truck was not the best on mpg but the best i have gotten out this truck was 12.9 mpg. I've also noticed my brothers truck whose is almost identical to mine except his is a 2500 2wd w/ nothing but exhaust and his seems to have a lot more "pull" then mine does even with these add ons. I've been reading forums on what kind of mpg this truck should be getting and I've read that guys that were running 33s or 35s weren't even getting that and mine is rollin stock. I've literally tried everything that I could think of to improve it but no minor tune ups helped. Any idea on y the loss of power and poor mpg?

Redtruck-VA · May 10, 2013

This always a good start for a argument, so I'll start it off, I lost both power and mileage when I put a Flowmaster on my Redtruck and got it back when I removed it. Pretty conclussive in my mind.

badblackram06 · May 10, 2013

Had a similar experience as Greg. Flowmasters have been said to be as restrictive, if not more, than the stock muffler.

Also you can try resetting the PCM. It always seems to help out.

NHDuckHunter8003 · May 11, 2013

12.9 MPG for mixed driving is pretty average I would say.

KGBIGCOUNTRY · May 11, 2013

Your 1500 Mega and his 2500 are built on the same setup, the gearing between the two might be making his feel like its pulling harder. Its had to say if thats it without seeing the spec sheets on the two.

Jmdoft91 · May 11, 2013

Well I was looking to replacing that flowmaster anyways just because I wasn't fond of the sound I got from it n I was gonna go to a magnaflow. Also the 12.9 was the absolute best that I've gotten out of the truck n that's straight highway miles. Hardly no city. When resetting the PCM will I know any signs that I had a successful reset? And what exactly should I be getting out of the truck with these add ons? Also the 2500 and mine are geared the same to my knowledge

truckin151 · May 11, 2013

I'm guessing you probably have 3.55 gears while your brother has 3.92 gears. reset the pcm ( disconnect the battery for 10-15min.) them take it out and either drive it like a grandma for a while OR drive it like you stole it. These trucks learn your driving style so driving it light should help relearn for a slight change in mpg, and driving it hard should help it relearn so it pulls a bit harder. don't expect dramatic increases in either but it should be a difference.

truckin151 · May 11, 2013

BTW despite what you may read about other vehicles, a ram with 392 gears will get better mpg and pull harder than one with 3.55's, and a truck with 4.56 rear gears will get better mpg than one with 3.92 rear gears. Specially one as big and heavy as yours.

Mine came with 3.92s, upgraded to 4.56s and along with a highly noticeable amount if extra pull to it, the mpgs jumped a good deal as well.

NHDuckHunter8003 · May 11, 2013

Yeah 12.9 seems low to me. I'll average in the 13's or 14's with 50/50 city and highway and I drive like a maniac. The skinny pedal is my enemy.

NHDuckHunter8003 · May 11, 2013

If you just bought it, it may be good to run a full tune up on it. That'll help for sure.

truckin151 · May 11, 2013

when were the plugs last changed?

Jmdoft91 · May 13, 2013

I don't think the plugs have been changed. It only has 63000 miles on it and how do I check to know for sure what the gears I have n the rear end?

truckin151 · May 13, 2013

yeah the plugs should have been changed by now. do a full tune up.

- pull the battery cable
- New plugs
- fresh oil
- drop the trans pan
- New/re-oil the air filter
- clean the throttle body
- balance/ rotate/ fill tires

The info for the hearing should be in the glove box if I remember correctly.

Jmdoft91 · May 15, 2013

Tried all of that n no improvement on mpg n idk bout pull cuz I've been driving it like a grandmaw... Even runnin premium as well

ST-8 · May 15, 2013

I used to get high 10s mid 11s when I bought my pig. After the mods before the cam I was able to pull near 13 in the city an 18 on highway. Now it's about 12/17 I changed my plugs at 80k they were the factory ones too. They didn't look bad but it was deff a noticeable difference.

Casper · May 15, 2013

Jmdoft91 said:
I bout my ram 1500 mega cab 4x4 w/ the hemi about 2 months ago and when I purchased the vehicle I noticed it had a K&N cold air on it along with a single in dual out flowmaster muffler as well. So I knew the truck was not the best on mpg but the best i have gotten out this truck was 12.9 mpg. I've also noticed my brothers truck whose is almost identical to mine except his is a 2500 2wd w/ nothing but exhaust and his seems to have a lot more "pull" then mine does even with these add ons. I've been reading forums on what kind of mpg this truck should be getting and I've read that guys that were running 33s or 35s weren't even getting that and mine is rollin stock. I've literally tried everything that I could think of to improve it but no minor tune ups helped. Any idea on y the loss of power and poor mpg?

Its a 2008 right? So you aren't the first owner. When were your plugs changed last? If more than 35K miles, or original, all 16 gotta go. That could help your Hwy miles a lot.
Other folks have already opined on your rear-end gears, muffler and resetting your PCM. Also (carefully)check that your AIT sensor in the intake hose is clean and not gunked with K&N CAI filter oil. When in doubt with a used Hemi, however, I would check your spark plugs--they don't run 100K mi like other engines. The preferred vendors to the right-->
can help you get the correct replacement and won't sell you some trendy crap the drift racers are all jazzed about instead.

Jmdoft91 · May 16, 2013

Ok well I just put a solid 400 miles on it after a fill up and running 65/70 most the way I saw a good increase in mpg after I reset the PCM and ran a few tanks of premium thru it. I got an averaged 14.6. Any recommendations of what brand plugs to go with? And also if I'm wanting to go magnaflow which muffler should I choose for the best performance? Also on that note I heard from a friend of mine who also owns a hemi that to put true duals on it from the manifold back would actually hurt it more then help. Is that true considering the fact of having the cold air?

truckin151 · May 16, 2013

as long as your pipe size is not to big and you put an "H" or "X" pipe in you should be with dual's. just don't do 2 straight pipes. Also since your truck is an 08' 1500 you have the mds system which kills have the cylinders while cruising and when that kicks in the exhaust tone sounds like crap IMO. get a tuner to turn that off, and run a performance tune and you should see a constant rise in performance and mpg.

truckin151 · May 16, 2013

oh and for plugs, the standard copper champion plugs are recommended.

Jmdoft91 · May 16, 2013

The mega cabs to my knowledge don't have the mds. So a performance tune after new plugs n muffler should help out tremendously?

Poor fuel economy/loss of power

Junior Member

Senior Member

Senior Member

Senior Member

Senior Member

Junior Member

Supporting Member

Supporting Member

Senior Member

Senior Member

Supporting Member

Junior Member

Supporting Member

Junior Member

Senior Member

U.S. Navy (Ret.)

Junior Member

Supporting Member

Supporting Member

Junior Member

Similar threads

Forum statistics

Share this page