Engine RPM and fuel economy

[rjanuszewski]

Just got a 2025 Lonestar with the SO hurricane engine. I noticed that the RPMs exceeded 2000 when going over 70 and there was a dip in fuel economy to around 15 and 16 MPG. I recently had a loaner with the same engine and transmission but noticed lower RPMs and obviously better fuel economy while driving the same. Not sure of where the RPMs should be when driving at 75 MPG where I have higher speed limits.

 

[FloridaSun]

Noticed same thing in my HO..sits at 2000...my 2020 would hit OD and drop to 1400 to 1500.....on the flip side hit the pedal and you better have something to hold onto...

 

[Scram1500]

Just got a 2025 Lonestar with the SO hurricane engine. I noticed that the RPMs exceeded 2000 when going over 70 and there was a dip in fuel economy to around 15 and 16 MPG. I recently had a loaner with the same engine and transmission but noticed lower RPMs and obviously better fuel economy while driving the same. Not sure of where the RPMs should be when driving at 75 MPG where I have higher speed limits.

My guess is your truck has a 3.92 and the loaner had a 3.21 gear ratio

 

[Skater]

My guess is your truck has a 3.92 and the loaner had a 3.21 gear ratio

I would agree with Scram1500. Does your truck feel like it has more pep of the start and is quicker to get up to speed than the loaner? If so, the gearing is likely what Scram1500 said.

 

[rjanuszewski]

It is the 3.92 in my truck. Had to look at the windows sticker.

 

[LITTLEREBEL]

It is the 3.92 in my truck. Had to look at the windows sticker.

From my knowledge, the 3.92 is a better all around gear.

 

[rjanuszewski]

Thanks

 

[Zeeya]

The rebel comes with 392 gears and as you mentioned at 70 mph I ran about 2000 rpms, where as the Laramie my bud has is the 321 gears. Like mentioned above it was down around 1550.

 

[jmr]

The S/O has 3.55 gears standard and 3.92 optional all H/O have 3.92. The 5th gen Ram with 5.7L had 3.21 gears standard and 3.92 optional the 3.6L had 3.55.

 

[TBHCPA]

RPM's are a small part of the equation. Temp, wind direction, drafting, tire pressure, wheel weight, and fuel quality are also factors. 3.92's get a bad rap but I don't buy it. I pick up my 2026 next week and will report back once I get past break in and can deliver some real life hand calculated MPG's. I had a 6.2 Trail Boss for 5 years and saw all sorts of varied MPG results depending on several factors.

 

[Trooper4]

I have 3.92's and with ocasional hughway/city, but mostly rural roads I get a pretty steady 19/20 empty. Any towing will drop me to 12/15 depending on if it is my boat or dump trailer. Like stated before, wind is a big problem, as these trucks are pretty well set up already, and anything can knock the mpg down.