2019 Classic 1500 4x4 with pentastar 3.6 mpg help please

[Dan_mccdc]

I am barely getting 18 mpg on the interstate.
The truck has around 60k miles. My totaled 2015 with the Hemi always got around 21mpg on the same stretch same speed. 75 mph. Same 8 speed and rear differential. The v6 engine appears to run perfect with 0 codes. We use the truck quite a bit and assumed the pentastar would get around 23mpg. 18 mpg is disappointing. What are some things I can look at? Idle hours and run hours are not accurate.

 

[Wild one]

I am barely getting 18 mpg on the interstate.
The truck has around 60k miles. My totaled 2015 with the Hemi always got around 21mpg on the same stretch same speed. 75 mph. Same 8 speed and rear differential. The v6 engine appears to run perfect with 0 codes. We use the truck quite a bit and assumed the pentastar would get around 23mpg. 18 mpg is disappointing. What are some things I can look at? Idle hours and run hours are not accurate.

Slow down and take the big tires and lift off it

 

[alpinegreenneon]

Dragging brakes?

 

[Dan_mccdc]

I do have an infrared gun so I will check that. Thank you. Even the tires are the exact siclze of the 15. No lift, all factory. Only difference is displacement.

 

[CanuckRam1313]

There could be multiple things going on here that are bringing down your mpg
As mentioned, maybe dragging brake(s) and or parking brake slightly engaged

What is the mileage

Is it time for a full service (based on the year indicated in your sig) - spark plugs, PCV valve, etc

Time to clean the throttle body, perhaps

Maybe a new engine air filter is needed

Use premium fuel and toss in a couple of bottles of Red Line SI-1 fuel system cleaner, fill with premium, run it to empty and refill with premium and run to empty, refill with premium and get an oil & filter change and continue to use premium fuel

Maybe time for a coolant change

Maybe time for a full fluid change (trans filter & fluid - front & rear diffs - transfer case)

Do you take the truck out and drive it spiritedly on a regular basis so it is not in Granny Mode

 

[Daw14]

I had both front calipers stick at different times, each time my mileage dropped.
I could smell a faint odor ,which I recognized as brakes dragging .
I shot the rotors with the infrared temp gun and the caliper was much hotter than the other side.
It was a couple years before the other side did the exact same thing.
I do watch the vacuum gauge, so that let me know my mileage was starting to drop.

 

[Toon12]

Low tire pressure or tires with high rolling resistance.
Dragging brakes.
Plugged air intake filter.
Driving over 65 mph. My trucks milage drops significantly at 70 mph and over.
My 2019 3.6L gets as high as 29 mpg on highway driven gingerly and at less than or at 65 mph. and about 18 mpg combined city/highway so there is room for improvement.

 

[DILLIGAF]

I don't even get 18 mpg in my Jeep JK with that pentcrap. You bought a truck with a V6 obviously it's going to be harder on fuel since that engine is way too small for that truck.

 

[Toon12]

My last two trucks have been the 3.6L V6 and at 305 Hp I found them quite adequate, unless you are towing a heavy load. My 2006 was a Hemi because I needed to tow and it was a pig on gas, 20 highway, and about 8 mpg around town. The 3.6L is much better for me at least.

 

[alpinegreenneon]

The only time I see my 3.6 mileage less than 21 mpg is when I'm towing. I'm in a rural area 30 miles from town. Long interstate trips, it's around 25 mpg.

 

[Dan_mccdc]

60,000 miles. No codes. Psi set at 40 on the tires. Ordered new air filter but looked great as the truck was purchased from a reputable dealer 3000 miles ago. Will clean the mas airflow sensor too. One interesting observation is that the tach on the truck looks like it is bouncing around 75 to 100 rpm while maintaing highway speeds. 8th gear 1800 to 1900 rpm. I am unable to hear any differences though. Will do it with or without the cruise. I am beginning to beleive that maybe just lowering it to 70 might gain me 8% as stated on another thread. Speed limit here in Oregon is 70 and most folks are running 75 to 80. It seems to be running perfect. No cat converter odor or hot brake pads that I have noticed. My temp gun will let me know for sure. I appreciate all the feedback. Great little motor I just am likely asking too much above 70. Will keep you posted.

 

[BenchTest]

I don't even get 18 mpg in my Jeep JK with that pentcrap. You bought a truck with a V6 obviously it's going to be harder on fuel since that engine is way too small for that truck.

That's not true. I routinely get 22-24MPG in my 4x4 3.6L truck. Driven 75-80MPH through rolling hills with 200-500lbs of cargo onboard, on numerous trips. The 3.6L is adequate for homeowner level. It's not a boat/RV towing engine by any means, but it does well as a basic truck engine.

 

[BenchTest]

60,000 miles. No codes. Psi set at 40 on the tires. Ordered new air filter but looked great as the truck was purchased from a reputable dealer 3000 miles ago. Will clean the mas airflow sensor too. One interesting observation is that the tach on the truck looks like it is bouncing around 75 to 100 rpm while maintaing highway speeds. 8th gear 1800 to 1900 rpm. I am unable to hear any differences though. Will do it with or without the cruise. I am beginning to beleive that maybe just lowering it to 70 might gain me 8% as stated on another thread. Speed limit here in Oregon is 70 and most folks are running 75 to 80. It seems to be running perfect. No cat converter odor or hot brake pads that I have noticed. My temp gun will let me know for sure. I appreciate all the feedback. Great little motor I just am likely asking too much above 70. Will keep you posted.

It's reasonable to expect low 20's from this configuration driving 75MPH. Add in lots of hills, wind, mountains, towing, or mechanical issues, then it'll start declining. A healthy truck with this config driven with fuel mileage in mind should be able to achieve low 20's regularly.

I drive mine from midwest USA out to Colorado, Utah, AZ, Wyoming a couple of times a year (rolling hills to mountains and back) and my trip average is about 22MPG running with about 300-500lbs of cargo (camping gear, offroad equip) over 3,000 miles. I get about 23-24mpg before the mountain portion and drop to high teens when pulling mountain grades or doing a lot of off-pavement driving. The truck doesn't like fighting wind, so if that factors in, I get a drop as well. Overall very satisfied from the MPG aspect of owning this truck.

 

[DILLIGAF]

That's not true.

35s , 4.88s , 2.5" AEV Lift and driving like I stole it says otherwise

 

[Ritchie_Rich]

Same heavy truck with a smaller engine. Worse mileage makes sense to me.
My wife’s 2011 Durango with the 3.6
Gets 20-22mpg on the interstate.

 

[star_deceiver]

18-19 is normal on the hwy. Hilly, windy 75mph usual speed. When I drive through BC and the mountains averaging 60mph, I can pull 22-24. If mileage and cost savings are that important, I’ll take the Fiat which easily gets 37mpg when driver retardedly.

Also, never believe the lie-o-meter.

 

[1979 300]

I don't know about the fuel in Oregon (where the O.P. is) but here in PA the winter blend gas that starts showing up this time of year will drop your MPG quite a bit.

 

[huntergreen]

When I hear of rpm varying for no reason, or bouncing around as posted, I think torque converter/ trans issue.

 

[Dan_mccdc]

This 8 speed is the light duty version. The 15 ram with the heavier version. It had a noticable locker when in final drive. Trans would appear to settle in 8th and lock. When it did rpms seemed to drop about 250 rpm if I remember correctly. The 19 version goes into 8 and doesn't drop rpm. It was a few months back when I noticed it. Just figured light duty trans and no biggie. Rpms appear to run higher in this trans. 1950 instead of 1750 rpms going 75 mph.
The trans doesn't slip though when I roll onto the throttle. Just pulls or shifts down.
I thought I read somewhere that the v6 trans was engineered to run a little higher in rpm too for the horsepower and torque. This forum is very helpful gents. Thank you again. The locker on the new trans may just engage sooner and that is why it isn't noticeable.

 

[Wild one]

The locker on the new trans may just engage sooner and that is why it isn't noticeable.

For future referance,the "locker" as you're calling it,is the torque convertor lock up,and the computor controls it.
I haven't really checked into the little 845's lock up rpms,but i'd think if anything it would go into lock up mode at a higher rpm,not a lower rpm as you're thinking