Poor gas mileage

[13bighorn1500]

My 5.7 Hemi has 73k and runs great with some performance modes. It is a 6 speed and wish I had a 8 speed.
I get 13 mpg on freeway and 6-8 mpg towing 23ft Springdale trailer about 7,000 weight depends on wind and I drive slow up grades.
Is this typical gas Mpg?
Is there any other mods to improve Mpg? Is it too much money to put in a 8 speed transmission?
I love this truck and new ones are expensive!!

 

[rouge_one]

I found changing your sparkplugs out will get u some better milage. I just done mine recently and noticed an improvement right of the gekgo.

I used to have 18 mpg before hand and after it went up to around 23 mpg

 

[CamperMike]

How fast are you driving? Do you have stock size tires? I get 18-20 freeway if I'm not driving too fast. It goes down quite a lot of us windy or you run 80 or above. Towing I get usually 7-10 mpg with a similar trailer to you. I usually keep it 65 or below. Go over 70 and 6-8 might be right. I do have the 8 Speed but I don't think that explains your unloaded mileage. It should only add like 1 or 2 mpg I think.

 

[caulk04]

Unloaded on the highway you should be around 15 I'd guess with previous Hemi and RFE trans experience. Loaded down with a 7k camper, I don't think you're going to get any better than you are. Keep up on maintenance and be mindful of driving habits, it is what it is.

Just remember, even if you improved your mileage by 20% (which is huge) it'll take a long time to pay back a big spend on parts.

 

[yrraljguthrie]

This won't be the reply you want, but by far the easiest way to increase gas mpg is simply to change your driving habits. One habit almost everyone has is when they see a red stop light they keep their foot on the gas for a while. That does absolutely nothing but use gas. You can't get through the light anyway, just coast up to the light. Many other habits don't speed the trip up but do use gas. Changing habits doesn't cost anything either. The change in habits doesn't have to be extreme. Two people can drive the same vehicle and one can easily without affecting traffic get 20% better mpg.

 

[Rlaf75]

You have an almost 400hp V8 with "performance mods" that has to move a 6k pound object with another 7k pounds of weight attached to it. I'm honestly surprised you're getting the mileage you are getting. There are several things that affect mileage, what I mentioned is probably the big one but, driving habits, road conditions, weather and altitude are also factors. Since there's not much you'll be able to do about the truck and trailer combo or the roads the next best thing would be to look at your driving habits and start there.

 

[fredwalters]

I have a 2020 hemi with ETorque 8 speed and get 13 to 14 mpg but the kicker is it has3.9 cogs, which really keeps the transmission in a lower gear longer.
My neighbor has the 3.31 cogs and gets 16 to 18 with identical truck and engine.
These numbers are a combo of local and highway driving.
Don’t change your transmission, you will never recoup that cost! I also always use Top Tier fuel.

 

[NCRaineman]

Going to second the "examine your driving habits" comment. My wife is the primary driver of our 2019 1500 Classic Hemi and averages 20MPG around town, with the factory 3.92 rear end.

 

[GSSS]

What are the performance mods?
What is the gear ratio?
What tires and what air pressure do you keep them at?

 

[Heatheroo]

Going to second the "examine your driving habits" comment. My wife is the primary driver of our 2019 1500 Classic Hemi and averages 20MPG around town, with the factory 3.92 rear end.

That's what I get with my 2019 Classic 5.7L 3.92 rear. Mixed HW/around town, my EVIC (yea...I know...), currently says 21.6MPG ave. (and that's with towing a 3500lb TT once or twice month). I always set my cruise control at 60MPH, accelerate slowly, coast to red lights, etc.. My average when I am actually towing is ~15-17MPG.

 

[David James]

My 5.7 Hemi has 73k and runs great with some performance modes. It is a 6 speed and wish I had a 8 speed.
I get 13 mpg on freeway and 6-8 mpg towing 23ft Springdale trailer about 7,000 weight depends on wind and I drive slow up grades.
Is this typical gas Mpg?
Is there any other mods to improve Mpg? Is it too much money to put in a 8 speed transmission?
I love this truck and new ones are expensive!!

Drive gently. Keep up with maintenance. No magic pill. Just enjoy the vehicle.

 

[HM_SanDiego]

As someone said - change the plugs & plug wires out, and as many have stated, drive with restraint - keep it under 75 on the freeway, no jack rabbit starts, coast when you can, use the cruise control as much as you can - you gettin 13 mpg’s on the Highway/Interstate tells me your right foot is heavy, a lot….

 

[Tominator223]

Try to use some Non ethanol fuel. When towing . Or all the time if possible. It’s just better. It is. It is.

 

[inuyasha-rules]

Fuel mileage is really random on these trucks. My dad gets 9 out of his 2019, I get 17 out of mine driving fairly aggressively, and my company truck gets 10. Various trim levels, all have the 5.7 and 6 speed transmission, only major difference is mines a 2wd single cab and the other two are 4wd crew cabs.

 

[NCRaineman]

9? You sure you don't mean 19?

If your dad has a 2019 model it has the 8-speed trans, not the older 6-speed. My 2019 averages 20.

17 is about what I'd expect out of an "aggressively" driven older truck with the 6-speed. The company truck must be really loaded down with tools and gear to get 10.

 

[NashTT]

Second on spark plug change. Changed mine at 76000 and saw an extra 3 mpg the next tank. Also runs better (smoother) and feels new again. One other mileage booster is to use 89 octane, but you’ve got to do the miles vs. dollars math on that one for yourself.

 

[Treburkulosis]

I am at 160k with the 6 speed. They don't get good MPG no matter what you change, no matter your driving habits, it just is what it is. I get if I am lucky 16-17 mpg on the hwy. 12-14 on around town. It's not about the MPG its about the smiles per gallon.

 

[Willie Mosher]

The 8 speed has same gear as 6 speed on top side, 8 speed add to gear bottom side, ( on 2500)

Any size truck, it takes BTU to pull
Trailer down the road, so
1/2 and 3/4 ton gets mpg pull
Same trailer.

 

[NCRaineman]

Second on spark plug change. Changed mine at 76000 and saw an extra 3 mpg the next tank. Also runs better (smoother) and feels new again. One other mileage booster is to use 89 octane, but you’ve got to do the miles vs. dollars math on that one for yourself.

89 octane definitely makes a difference, as that is the recommended fuel grade for the engine. Yes it CAN run on regular, but the computer will pull timing to prevent knock so you end up losing power and economy.

Spark plugs, YES. If you check the owners manual I believe it recommends replacing at 65k... and there are sixteen of them.

 

[MRFREEZE57]

Gas mileage is directly related to the weight of the right foot.