6.4L performance and efficiency improvements?

akburwell · Apr 3, 2017

Hi y'all! First post over here but have been hanging out over at the Ecodiesel group.

I'm making the shift from the small diesel to a 6.4 Hemi 2500 to accommodate a growing family of toys and gas engine to have less hassle in around town use.

I'm wondering what are the low hanging fruit recommendations on that 6.4L Hemi to get better fuel economy? I'm guessing cold air intake and exhaust but wanting to know specifically what people have experience with and what the expected gains could be. Thanks! -Adam

sandawilliams · Apr 3, 2017

akburwell said:
Hi y'all! First post over here but have been hanging out over at the Ecodiesel group.

I'm making the shift from the small diesel to a 6.4 Hemi 2500 to accommodate a growing family of toys and gas engine to have less hassle in around town use.

I'm wondering what are the low hanging fruit recommendations on that 6.4L Hemi to get better fuel economy? I'm guessing cold air intake and exhaust but wanting to know specifically what people have experience with and what the expected gains could be. Thanks! -Adam

Google cold air intake and you will find many test videos showing CAI do nothing for mileage or power.

Sandbox · Apr 3, 2017

The only thing that will help the 6.4 get better MPG is to park it. I quit caring about gas mileage the day I drove mine home.

MADDOG · Apr 3, 2017

Intake, exhaust and a custom program all work well in the 6.4L.

AFE finally introduced their cold air intake which looks really, really good. I didn't get a chance to try one out because my truck was recently totaled. I wasn't going to buy anything else but their kit as I have experience with their stuff on other vehicles and it works really well.

I replaced my muffler with a Magnaflow unit for more air out.

I also took advantage of the package deal of a DiabloSport I2 programmer with custom tune by Hemifever from Moe's Performance and it really woke up the truck.

I never got the chance to measure any mileage gains but as far as performance the truck was a real blast to drive.

As far as mileage goes, I never measured it. I decided it was a waste of my time given the size of the rig and the displacement/power of the engine. There's no way it was ever gonna be a good figure. If I had to guess, I'd say I got maybe 1.5 MPG better in highway driving. Around town? Nothing would help that as it's a large, heavy truck.

akburwell · Apr 3, 2017

Sandbox said:
The only thing that will help the 6.4 get better MPG is to park it. I quit caring about gas mileage the day I drove mine home.

Are the numbers on Fuelly.com pretty accurate? 10-12mpg averages that is.

gustheram · Apr 3, 2017

akburwell said:
Are the numbers on Fuelly.com pretty accurate? 10-12mpg averages that is.

Yeah that's about right. I average around 11-12 in mixed driving. Before I put aggressive tires on, I was getting 16, maybe 16.5, on the highway. With the aggressive tires I'm running right now, I'm down to 15-15.5. As others have said, it's a big truck with a big motor, and I'll add it has the aerodynamics of a barn door. There's literally nothing you can do to get good mileage out of it. The best thing you can do for your sanity is to just not care about it. I tried to care for about a year and then I just gave up because what's the point.

Sandbox · Apr 3, 2017

Unless you lower your standards for good mileage. It's a big heavy truck with a big motor that is made to pull big heavy things. I've had mine on one road trip and the computer read just a little better than 16mpg. During the week, depending on how far I stick my foot into it, I get 12-13. And couldn't be happier!!

THETANK · Apr 3, 2017

I used to get in the mid 20's with my 6.4 as long as I kept it at 60 mph, errrrr hang on that is with the Challenger SRT8 lol

akburwell · Apr 3, 2017

gustheram said:
Yeah that's about right. I average around 11-12 in mixed driving. Before I put aggressive tires on, I was getting 16, maybe 16.5, on the highway. With the aggressive tires I'm running right now, I'm down to 15-15.5. As others have said, it's a big truck with a big motor, and I'll add it has the aerodynamics of a barn door. There's literally nothing you can do to get good mileage out of it. The best thing you can do for your sanity is to just not care about it. I tried to care for about a year and then I just gave up because what's the point.

Thanks. Definitely understand that it's a big truck and a big engine. Typical salesman at my local dealer said a guy who works in the shop has a 6.4L CC 4wd with a chip, exhaust and intake claiming 22 mpg's on the hwy... I was curious if others on this forum have done similar mods with similar results because my first instinct was he's full of it!

gustheram · Apr 3, 2017

akburwell said:
Typical salesman at my local dealer said a guy who works in the shop has a 6.4L CC 4wd with a chip, exhaust and intake claiming 22 mpg's on the hwy...

Bwahahahahahahahaha! No but seriously ..... bwahahahahahaha! Ok I'm done now. For real though, I bet it actually would be possible to get 22 on the EVIC if he's running a 265 or 275 series street tire inflated to max psi and doing no more than 60mph. 22 on the EVIC would probably translate into about 20 hand calculated though. Still damn good, but most people aren't sticking to 60mph. At real world highway speeds, I don't think there's anything anyone could do, short of catching a 40mph tail wind, that would get 22mph hand calc'd out of one of these beasts. Sticking to 55mph on a 60 mile trip I saw my EVIC go up to 21 one time (I only did it because the speed limit was 50 lol). Hand calculated, I was about 19 mpg for that trip (still had the stock TransJunks on then). The general consensus seems to be that stop and go or anything over 60 and the mpg drops like a brick.

mohemipar · Apr 3, 2017

I just ordered a 2500 6.4 Laramie, and I'm going into it with the mindset of not worrying about MPGs. I would actually be very happy getting 16 on the highway and 11 in the city. My 5.7 1500 was doing high 10s in the city all winter and has just got up to 12.0 even with the slightly warmer weather. I never see better than high 12s in the city even during the summer. And all of those are actually worse in reality because that is what the EVIC is saying lol.

Correct me if I'm wrong, but with the retirement of the Viper, I believe the 6.4 Hemi is currently the largest NA gas engine currently in production. So really, 16 MPG out of a 7500 pound rolling brick with a 392 Hemi is pretty damn good.

I regularly get 15 city and can top 20 on the highway without even trying very hard in my Scat Pack. No complaints from me.

akburwell · Apr 3, 2017

mohemipar said:
I just ordered a 2500 6.4 Laramie, and I'm going into it with the mindset of not worrying about MPGs. I would actually be very happy getting 16 on the highway and 11 in the city. My 5.7 1500 was doing high 10s in the city all winter and has just got up to 12.0 even with the slightly warmer weather. I never see better than high 12s in the city even during the summer. And all of those are actually worse in reality because that is what the EVIC is saying lol.

Correct me if I'm wrong, but with the retirement of the Viper, I believe the 6.4 Hemi is currently the largest NA gas engine currently in production. So really, 16 MPG out of a 7500 pound rolling brick with a 392 Hemi is pretty damn good.

I regularly get 15 city and can top 20 on the highway without even trying very hard in my Scat Pack. No complaints from me.

Yeah, I'm going to be stoked with 16+ mpgs on the hwy considering I'm going for a 6.4L in a Power Wagon... a little taller and 33" Duratracs. Anything over single digits in the city would make me feel okay as well considering we live in a small town. After the truck get's some proper overland armor I may "open it up" and "let it breath" some day to see if helps but at that point the truck will be heavier with bigger tires.

Viper was the largest engine...http://jalopnik.com/the-worlds-ten-largest-engines-509258535 At least I'm not operating that boat engine... 39 barrels of oil per hour!

nukegm · Apr 4, 2017

i like my 6.4 tradesman 2500

it has 3.73 gears

if i could do it over again, i would order the same truck with 4.10 gears

or the cummins

currently get 12 mpg at 9300 feet - 5500 feet elevation

spending 80 bucks per week on mid grade - the 80 per week would easily cover the price diff between the gasser and the diesel

cheers comrades!

Bigdaddy · Apr 4, 2017

Yeah I do love my 6.4L 2500 and the best I have got was 17 mpg highway and 11-12 in the city, the 1/2 that I had was about the same if not less and I have more truck with the same or better mileages.

I don't think that it get no better than this, I love it

BTW: I have 4.10 gears.

GsRAM · Apr 4, 2017

akburwell said:
Are the numbers on Fuelly.com pretty accurate? 10-12mpg averages that is.

I'm averaging around 10mpg on my mostly back roads commute to and from work and i drive like there's an egg on the skinny pedal.

I don't really mind either. I bought this rig to have a big, heavy HD truck to haul my TT. I figure I'll burn up all that extra fuel those toyota prius are saving. Lol!

The 6.4 is thirsty, but man, I can tell she has a lot of juice! And I've not had it past 1\2 throttle yet

Mchurch52 · Apr 4, 2017

I average between 14-15 MPG with a mix of city/hwy on my daily commute. The average when highway only is around 17 MPG when keeping the speed no more than 70 MPH. As others have said, anything over 70 MPH and drag really starts eating into fuel economy. I have a HF tune on mine and stepping on the gas is lots of fun, but I usually try to minimize getting on the gas hard at stop lights just because I can't stand watching the lie-o-meter drop like a rock.

sandawilliams · Apr 4, 2017

GsRAM said:
I'm averaging around 10mpg on my mostly back roads commute to and from work and i drive like there's an egg on the skinny pedal.

I don't really mind either. I bought this rig to have a big, heavy HD truck to haul my TT. I figure I'll burn up all that extra fuel those toyota prius are saving. Lol!

The 6.4 is thirsty, but man, I can tell she has a lot of juice! And I've not had it past 1\2 throttle yet

The best I've gotten is 17 MPG driving 65. In town I get about 2 gallons to a mile.

mowin · Apr 4, 2017

Just finished a 1600mi round trip. NY to MI. Ran 5-7 mph over the speed limit, so top was 76mph.
Hand calculated I got 16.8. Stock 3500 SRW 3:73's. It may have done better, as there's only 2500mi on the clock after the trip. This is my 2nd 3500 with the 6.4.

akburwell · Apr 4, 2017

nukegm said:
i like my 6.4 tradesman 2500

it has 3.73 gears

if i could do it over again, i would order the same truck with 4.10 gears

or the cummins

currently get 12 mpg at 9300 feet - 5500 feet elevation

spending 80 bucks per week on mid grade - the 80 per week would easily cover the price diff between the gasser and the diesel

cheers comrades!

Would definately consider the CTD but 90% of my driving is around town and keeping it under 55 mph. The bigger 70+ hwy out of town is a once a month. This was the problem with my Ecodiesel... kept getting the "Exhaust filter 90% full, drive at hwy speeds until empty" messages weekly forcing detours around town instead of through town. The CTD guys and gals seem to think that engine wouldn't be any better with regen frequency but perhaps y'all know something I don't?

mohemipar · Apr 4, 2017

With the Cummins and even the baby EcoD, you will have issues with the computers if you do a lot of city driving and or short trips. The engines themselves also dont like a lot of idling. And all of the emmissions garbage on there is what causes all of the trips to the dealer and squeezes the life out of the motor. So IMO, you have to really need the true benefits of the CTD over the 6.4 Hemi to buy one. Its a shame because they are amazing trucks and Cummins makes the best diesels. Deleting it is great option, but a lot of states require emissions testing.

6.4L performance and efficiency improvements?

Junior Member

Senior Member

Senior Member

Out Exploring Arizona

Junior Member

Senior Member

Senior Member

Senior Member

Junior Member

Senior Member

Senior Member

Junior Member

Senior Member

Senior Member

Senior Member

Member

Senior Member

Senior Member

Junior Member

Senior Member

Similar threads

Forum statistics

Share this page