Bad Economy With Hemi 2500

[Alamedasam]

I have a 19’ 2500, 6.4 4X4. According to the fuel & mileage screen it’s only getting 6.2 to 10.1 mpg at 55mph on highway!

It only shows about 222 miles to empty upon just filling up & zeroing the screen.

Anybody have any ideas or have the same issues.

I’ve talked with others who say they get anywhere from 10. To 12.5 city & 13.0 to 14-16 highway.

What should I expect to see?

Thanks in advance!

 

[rzr6-4]

First things first, go fill up and then drive for a while and then next time you fill up calculate it manually to see if what your dash is saying is even halfway correct. Most people say there's a small difference between manual calculation and what the screen says but they should at least be close.

 

[Docwagon1776]

Any mods? Tires?

That seems way low. I can get 17+ at 55mph in my PW on summer gas.

 

[Dean2]

I have a 19’ 2500, 6.4 4X4. According to the fuel & mileage screen it’s only getting 6.2 to 10.1 mpg at 55mph on highway!

It only shows about 222 miles to empty upon just filling up & zeroing the screen.

Anybody have any ideas or have the same issues.

I’ve talked with others who say they get anywhere from 10. To 12.5 city & 13.0 to 14-16 highway.

What should I expect to see?

Thanks in advance!

Lifetime average on my 6.4, hand calculated, is 15.65 mpg. Best tank was over 19 mpg. If your readout is close to right there is something that needs fixing.

A simple search of this forum would turn up more than 50 recent threads talking about your problem of poor fuel economy and how to diagnose it. Here is just one of them.

Horrible fuel consumption (6 mpg)..from14 to 6 rapidly.

My 1966 ram 1500 5.2 L has dropped from 13-14 mpg to about 6 mpg over last few mos. It idles fast some days and sputters and shudders on others. No fuel smell but only get about 100 mi / tank and I live far far in the boonies. I almost can't afford to drive it? What is likely the problem...

www.ramforum.com

 

[dieselscout80]

I have a 19’ 2500, 6.4 4X4. According to the fuel & mileage screen it’s only getting 6.2 to 10.1 mpg at 55mph on highway!

It only shows about 222 miles to empty upon just filling up & zeroing the screen.

Anybody have any ideas or have the same issues.

I’ve talked with others who say they get anywhere from 10. To 12.5 city & 13.0 to 14-16 highway.

What should I expect to see?

Thanks in advance!

How many miles are on your truck?

Is your truck still stock or is it modified (e.g., tires, lift, winch)

Have the spark plugs been changed?

 

[Alamedasam]

Only has 83,k miles. Had been tuned about 1,k miles ago. Runs great. Had wider-taller tires installed just before I bought it.

 

[dieselscout80]

The larger tires are not helping your fuel economy.

Also, was the tire size increase changed in your truck’s computer as that can affect it odometer, shift points to name two things and these may affect mpg?

Also the tire tread can affect fuel mileage a highway type tread gets better mpg than a mud tire.

Skinny pedal application rate really changes/affects fuel mileage in that more smiles per mile equals less mpg.

 

[Rlaf75]

Only has 83,k miles. Had been tuned about 1,k miles ago. Runs great. Had wider-taller tires installed just before I bought it.

When you say "tuned" are you talking about spark plugs or an actual computer tuning for more "performance"? @dieselscout80 pretty much hit the nail on the head

 

[Daw14]

Fuel quality can impact mileage .

 

[dieselscout80]

Here’s what the computer says I did over the last almost 5k miles (my oil change interval).

 

[Daw14]

Here’s what the computer says I did over the last almost 5k miles (my oil change interval).

The mileage reading from the truck is most likely off by a couple miles .
And it always claims you get further, for some reason only Mopar executives have the answer.
Calculated by person will give a more accurate picture.

 

[dieselscout80]

The mileage reading from the truck is most likely off by a couple miles .
And it always claims you get further, for some reason only Mopar executives have the answer.
Calculated by person will give a more accurate picture.

Very true, but it gives a rough idea.

 

[Dean2]

The mileage reading from the truck is most likely off by a couple miles .
And it always claims you get further, for some reason only Mopar executives have the answer.
Calculated by person will give a more accurate picture.

True, though my 2500 is most times high and but also occasionally lower than hand calculated. It is always in the ballpark, rarely out more than 1 mpg and I track 100% of my fills and record actual vs EVIC calcualted.

The issue is, the OP's EVIC mileage is 10 or less, so likely around 9 on average. I have never had mileage like that unless I did a ton of idling or was in low range for the whole tank. Highway at 55, his EVIC should be 16+. Tells me he has an issue.

 

[dieselscout80]

I have a 19’ 2500, 6.4 4X4. According to the fuel & mileage screen it’s only getting 6.2 to 10.1 mpg at 55mph on highway!

It only shows about 222 miles to empty upon just filling up & zeroing the screen.

Anybody have any ideas or have the same issues.

I’ve talked with others who say they get anywhere from 10. To 12.5 city & 13.0 to 14-16 highway.

What should I expect to see?

Thanks in advance!

Question what are your coolant temperatures when engine is fully warmed up?

 

[Marshall]

you list a 2019 5.7 hemi , but now talking about 6.4, So I presume one a misprint?
that mileage sound like you are dragging around a big trailer. Have a look at brakes, but if they where dragging bad, you would smell them. Maybe the tune is screwed up.

 

[Alamedasam]

Thanks everybody. I realize tire size will have an effect on mpg. My buddies both have the same tire & wheel combo.

I have tried to find someone that can reprogram the computer for tire size. Nobody has this truck-engine combo software. Local dealer don’t have it either.

 

[Alamedasam]

Thanks everybody. I realize tire https://www.ramforum.com/threads/bad-economy-with-hemi-2500.225050/reply?quote=3091470size will have an effect on mpg. My buddies both have the same tire & wheel combo.

I have tried to find someone that can reprogram the computer for tire size. Nobody has this truck-engine combo software. Local dealer don’t have it either.

 

[Docwagon1776]

Thanks everybody. I realize tire size will have an effect on mpg. My buddies both have the same tire & wheel combo.

I have tried to find someone that can reprogram the computer for tire size. Nobody has this truck-engine combo software. Local dealer don’t have it either.

There's several options to do it yourself. Probably the easiest is: https://www.zautomotive.com/collections/tazer or a slightly cheaper option is the AEV ProCal SNAP if you don't want or need the rest of the Tazer functions.

 

[star_deceiver]

I have tried to find someone that can reprogram the computer for tire size. Nobody has this truck-engine combo software. Local dealer don’t have it either.

Try a route like this. Fill up in Sylmar. Get on the I-5. Set your cruise for 80mph, a little slow for this particular route but it’ll get you there. Turn around at wheeler ridge and come back. Refill at the same station in Sylmar. Divide the 120mile trip by gallons used. You now know what you’re going to get for real world mileage and how much your speedometer and odometer are off.

 

[markabby]

when you're driving at exactly 55mph, what RPMs are you at? And does your overdrive kick in at that speed?