[jbaugh]

My truck is the 2011 Outdoorsman with the Hemi and I've had it since Sept. 2011. When It was brand new it got the mileage that is bragged about on the TV ads... 15-20 MPG.
The first mod I did was install a K&N cold air intake system. Big, big increase in horsepower and very noticeable increase in MPG's.
After reading more mods in these forums I decided to change the exhaust up a little. I purchased a new "Y" to eliminate the constriction created by the factory bends in the exhaust pipes. At the same time I purchased a Magnaflow muffler to replace the stock one. It sounds and runs awesome but the mileage went to the ditch! At first I thought it was just me putting my foot into too much to hear how fine it sounds. But after several months of honestly not dogging it and even using the cruise on the highway, the best it will get is 17-18 highway.
I'm considering putting the stock muffler back on.
Does anyone have any recommendations and or had a similar outcome after virtually eliminating any back pressure in the exhaust?
Thank you in advance!

 

[11bighornblue]

I am wondering about this too.. I got the y pipe and mufflex muffler. I am using a mpg app on my i-phone. I am averaging 15-16mpg. I drive 38 miles one way to work about 80% of it is Highway

 

[CHVYKLR]

if I keep it under 70 mph I still knock down 19 mpg on the hwy

 

[11bighornblue]

if I keep it under 70 mph I still knock down 19 mpg on the hwy

Ill try this. its seems I have tried everything but my drive to work today I will keep it under 70

 

[roadrnnr]

For me it seems to be the gas I use also Summer 19-20 winter 15-16.

Sunoco seems to be better than Mobil for me

 

[THasse]

I've definitely noticed a difference in fuel companies. Shell seems to work well for me, whichever company they get their fuel from, I'm not sure whose it is. Winter here is definitely worse than summer cuz of the additives, etc. I don't have MDS, but I drove it for a while at 60, 65, and 70 on the same road, same area, so hills weren't a factor etc. Between 60 and 65, there was some mileage drop, but it dropped significantly between 65 and 70. At 63 mph, seems to be a real sweet spot in the mileage for some reason, atleast on mine...

 

[TNC]

It's true that most winter fuel blends bring on a frequency of fuel mileage complaints, so I'd wait until the seasonal fuel changes back to make a final determination if fuel mileage actually went down because of the performance mods.

That said, I'd find it hard to believe that a higher flow intake and exhaust would negatively affect mileage. About the worst it can do is make no difference at all. Now, I'm talking about intake and exhaust mods in the area of a higher flow muffler, moderate piping mod like the y-pipe, opening up the air intake volume, and installing a higher flow filter or filter system. I do think that many header systems when coupled with a much higher flow exhaust system downstream can actually affect mileage, because some of the designs optimize performance at the higher rpm range at the expense of some performance and/or fuel economy at cruise speeds...and then some headers are designed to build low and mid-range power without providing huge gains at the higher rpm range.

I think it would be very rare for a better flowing exhaust...taking headers out of the equation...coupled with a higher flowing intake system to cause a loss in fuel economy. The stock muffler has to meet very strict sound regs and so does the intake system at the OEM level. Opening up both of them in a reasonable manner is usually always within the parameters of the computer to compensate for and provide a reasonable benefit in the process. Another way to look at it is that if you get a small performance increase with no negative effect to fuel mileage, that alone would be a worthy outcome. Unless an aftermarket muffler, pipe, or intake system was of an incredibly bad design, I tend to doubt any drop in fuel mileage is attributable to them.

 

[huntergreen]

wonder if the increased airflow via cai is telling the ecm to increase the amt of fuel into the injection system.

 

[TNC]

wonder if the increased airflow via cai is telling the ecm to increase the amt of fuel into the injection system.

Interesting thought, but wouldn't the exhaust sensors read the end result of too much unburnt fuel and have the computer react accordingly? Generally I think an engine that has an effectively modded intake and exhaust will indeed require more fuel to mix with the increase in air flow and increased power. But...this condition also usually brings to the table the opportunity for smaller throttle openings during operation, less downshifts, and generally better driveability. So, you usually either get additional power at no cost...no mileage increase...or you get the additional power and a small fuel mileage increase. It seldom results in less mileage when the mods were done correctly.

 

[Bighert3rd]

The first mod I did was install a K&N cold air intake system. Big, big increase in horsepower and very noticeable increase in MPG's.

Interesting...At the very best a CAI would give you a 15 HP increase and in a truck that weighs as much as a RAM this would be next to impossible to feel. Sorry not trying to come off like a jerk, but you would have to add a substantial amount of HP to really feel a big big increase. Did you have it put on a dyno? This was my first mod as well and I felt no difference besides maybe a little better throttle response.

After reading more mods in these forums I decided to change the exhaust up a little. I purchased a new "Y" to eliminate the constriction created by the factory bends in the exhaust pipes. At the same time I purchased a Magnaflow muffler to replace the stock one. It sounds and runs awesome but the mileage went to the ditch!

I always thought that the mufflers did not affect the back pressure. From my understanding the muffler's only job is to quiet the noise. Your cats are what provides the back pressure. I could be way off here, but I know I heard that somewhere. Just for comparison...I deleted my Y pipe and have true duals with 2 straight through mufflers and X pipe, no resignators and I have not expierienced any loss in MPG's. There are so many factors that affect MPG's that to get a constant number would be hard. Like others said different gas stations, additives, weather, wind, traffic, etc. can reduce or increase your MPGs.

 

[wbowyer]

As long as you have the factory pipes and cats there really isn't and reason to get lower MPG's than with the OEM components. Better flow = better efficiency. Make sure your oil is in good condition and that you treat the fuel system every once in a while (especially when the fuel blends start to change). Also, after adding the CAI and muffler did you reset the computer by disconnecting the battery? This allows it to correct the fuel/air mix.

 

[Emorris69]

I am been running a K and N intake and duel magna flow system for almost a year now and i have noticed a better high way milage and city cruising numbers. The problem i find is that I end up racing people in morning traffic people heat the truck and I end up racing city blocks. Which kills the gas millage

 

[ArmyofOne]

My truck is the 2011 Outdoorsman with the Hemi and I've had it since Sept. 2011. When It was brand new it got the mileage that is bragged about on the TV ads... 15-20 MPG.
The first mod I did was install a K&N cold air intake system. Big, big increase in horsepower and very noticeable increase in MPG's.
After reading more mods in these forums I decided to change the exhaust up a little. I purchased a new "Y" to eliminate the constriction created by the factory bends in the exhaust pipes. At the same time I purchased a Magnaflow muffler to replace the stock one. It sounds and runs awesome but the mileage went to the ditch! At first I thought it was just me putting my foot into too much to hear how fine it sounds. But after several months of honestly not dogging it and even using the cruise on the highway, the best it will get is 17-18 highway.
I'm considering putting the stock muffler back on.
Does anyone have any recommendations and or had a similar outcome after virtually eliminating any back pressure in the exhaust?
Thank you in advance!

Sounds like someone has a case of "cant-keep-foot-out-of-it-itis"

Its ok, I get it to.

As far as spending money to boost mpg, I see little point. The truck is not going to get much better than it was designed to, no matter how much money you throw at it. If your sole purpose behind doing mods is to get better fuel economy, You will be severely dissappointed.

I just do it cause its fun. I...Cant...Stop...

 

[Hex]

There's a lot of great info in this thread relating to basic performance mods.

I agree with ArmyOfOne. After getting new toys put on your truck, especially ones that make it sound more like a racecar. Whether there is a real impact on HP or not, the sound increases the feeling of the butt-dyno and that leads to heavier right feet. very common.

 

[dkerr24]

The best performance mod you can make to increase MPG is replace the NUT BEHIND THE WHEEL. Under ideal conditions, I have received 23.7 mpg in my 5.7L Hemi, but you gotta keep the speed under 65mph!

 

[mustang8918]

I would agree, speed is the biggest culprit.

 

[Colorado700R]

If you invested in performance mods that make the machine sound meaner.....you're going to want to hear it...therefore your foot is down more often.

 

[Guest]

Consider yourselves lucky

I have tried every damn alternative I know of...I've run 91 octane, 89, and 87. I've put it on cruise control on the freeway, and carefully watched the take-offs from the lights to maximize fuel efficiency, and I have YET to get better than 16 Mpg, and that was done with almost all freeway driving at 65 mph on cruise. Although I do have to consider that most of my driving is around town, and our town has more than it's share of stoplights, I should do better than 12 when driving around town. I even put a really nice Snug Top cab high shell on it which should have reduced some of the air resistance and given it a more aerodynamic contour when on the road.

I'm a bit discouraged when I read all these posts about getting 18 to even as high as 22...and I can't seem to break the 16 barrier. I think I'll take it back to Dodge and see if they can tune it a bit better. There's no reason I should be getting $hitty mileage like this after conscientiously trying to maintain a light foot on the accelerator. I even bought the 2 wheel version, so I have less weight than most of you who are running 4X's. :4-dontknow:

 

[Hex]

I tried driving at 64mph for a couple days on my highway trips, as i read that that was the optimal speed to improve gas mileage. I noticed a slight improvement, but I seem to do better with the cruise control set at 70. Seems i can stay between 17.5 and 18mpg by the end of the tank.

The best performance mod you can make to increase MPG is replace the NUT BEHIND THE WHEEL

I actually stopped to think of which nut this would be, until I realized which wheel you were talking about...

 

[dkerr24]

I have tried every damn alternative I know of...I've run 91 octane, 89, and 87. I've put it on cruise control on the freeway, and carefully watched the take-offs from the lights to maximize fuel efficiency, and I have YET to get better than 16 Mpg, and that was done with almost all freeway driving at 65 mph on cruise. Although I do have to consider that most of my driving is around town, and our town has more than it's share of stoplights, I should do better than 12 when driving around town. I even put a really nice Snug Top cab high shell on it which should have reduced some of the air resistance and given it a more aerodynamic contour when on the road.

I'm a bit discouraged when I read all these posts about getting 18 to even as high as 22...and I can't seem to break the 16 barrier. I think I'll take it back to Dodge and see if they can tune it a bit better. There's no reason I should be getting $hitty mileage like this after conscientiously trying to maintain a light foot on the accelerator. I even bought the 2 wheel version, so I have less weight than most of you who are running 4X's. :4-dontknow:

I think the SnugTop may be part of your issue. The aerodynamics of the truck were not optimized for the use of a shell topper. I had the same issue with a previous truck that I owned when I added a shell topper.

Darin