Difference in gas mileage between the 3.21 and 3.92?

[Ram1500OwnerMaybe]

Majority of trucks come with the 3.92 gear ratio.
The ones with 3.21 aren't the ones I prefer due to color, model, options, etc....
No plans to haul/tow so trying to stick with the 3.21, but curious to know the gas mileage difference people are seeing between the 3.21 and 3.92 for daily use driving in case I have to opt for the 3.92.

 

[Deleted Account]

I run the 3.21 in my BigHorn. Only 3.5k miles so far, but every tank is between 19 and 21 MPG (real calculation, not the lie the truck tells). My commute is half city, half highway, but I get the same numbers on a road trip at 70.

 

[Oliver392]

If you do a lot of hwy driving, and you don't have any plans of larger wheel/tires and lifting the truck, consider the 3.21. The difference at 70 mph is approx. 4-500 rpm. For me it makes for a more comfortable and relaxing hwy drive. And possibly an extra 1-2 mpg. ( Assuming same wheels/tires, lift or no lift, same speed). If possible, test drive a 3.92 truck at 70 mph and then do the same with a truck that has 3.21 gears. I did just that before I ordered my '16 Laramie.

I have 3.21 gears in my '16 Laramie 4x4 CC. About 10% of my driving has been towing my 20' enclosed car trailer. About 5500 lbs with a car in it. No issues. And that is with towing up and down some decent grades through PA and Western NY. If I towed a lot more and pulled 2000lbs more I would have 3.92 gears.

One thing that I should notice between my '16 and the '20 is the difference in cruise rpm. For '19 RAM went to a 32" diameter tire on the Laramie (275 55 20) the '16 has 33" tires (275 60 20). So for me the 3.21 gear might feel more like (without doing the math) a 3.3xx. Maybe... I have yet to read anyone mention this with the 5th Gen vs the 4th Gen.

Don't overlook ordering a truck to get exactly what you want. I Ordered my 2020 Limited on 9/23 and it is currently in transit.

 

[Bigtone]

My 2010 Ram had 3.92 gearing and on trips from Pa to Florida (all interstate, fuel stop to fuel stop) it would get around 18-19 mpg. I traded in on a 2014 Laramie, same 20" wheels/tires, quad cab, only difference was 3.21 gears (and of course 8 speed trans, which I do not believe matters in the highest gear on highway). The 2014 got around 21 to 22 mpg, and it may have been slightly heavier. I'm hoping my 2019 Laramie with 18" wheels gets even slightly better than the 2014. One trip to NY and back with only 1k miles on it got 21.8 mpg.

 

[2wd]

city and mixed driving is a wash on mpg. Pure highway with light loads the 3.21 can return better mpg.

I have 3.21 and have recorded 22-24mpg averages on 500+ mile round trips on the east coast (90% hwy mile). See my past posts for details/screenshots.

rebels and some off road package trucks are reporting significantly worse mpg.

i have also towed 8k with this setup very comfortably. lower numerical gears in these trucks with 8/10 speed transmissions are win win. would recommend.

 

[AndreiV]

Pure city - 13 mpg.
Pure highway - up to 20 mpg @ 70mph avg.

 

[C.E.Divine]

Before my ORP truck with 3.92's was broken in, it was getting around 14-15 mpg combined. Now I've got about 28,000 miles, and get around 20 mpg combined. I do an even split time-wise of city and highway (a little over an hour of each a day) and calculate my mileage by hand. The computer is close, but consistently under by about .3mpg.

 

[Rob5589]

There doesn't seem to be a significant difference between the two based on what people post. Mine has the 3.21 and ave 18.5-19 of mixed driving, 20.6 was the best pure hwy running 75-80 mph. Around town only it drops off by about 3-4 mpg.

 

[ddharris]

My 2010 Ram had 3.92 gearing and on trips from Pa to Florida (mostly interstate) it would get around 18-19 mpg. I traded in on a 2014 Laramie, same 20" wheels/tires, quad cab, only difference was 3.21 gears (and of course 8 speed trans, which I do not believe matters in the highest gear on highway). The 2014 got around 21 to 22 mpg, and it may have been slightly heavier. I'm hoping my 2019 Laramie with 18" wheels gets even slightly better than the 2014. One trip to NY and back with only 1k miles on it got 21.8 mpg.

Did your 2010 have cylinder deactivation?

 

[2wd]

There doesn't seem to be a significant difference between the two based on what people post. Mine has the 3.21 and ave 18.5-19 of mixed driving, 20.6 was the best pure hwy running 75-80 mph. Around town only it drops off by about 3-4 mpg.

There is a difference, but only for highway mileage.

Bring your speed down to 65-75 and you should see 22+ mpg with 3.21. However, literally YMMV. I see you have the ORG. The 1 inch lift may be hurting your aero/drag.

 

[ddharris]

I really wouldn't worry about maybe 1 mpg difference in a 60K truck. Either rear end set up is fine really.

 

[ddharris]

Adding in all the different variables makes this a really unbelievably subjective discussion.

 

[EJanx07]

I have a Big Horn w/ ORG with 2” Level Kit.
I average in mixed City/County Road: 15.4mpg. I’m not real light on the pedal...
Freeway/Highway 65-70mph: 21mpg.
Stock Falken Wildpeak AT 275/65/18 (32” tires)
I’m sure the mpg will go down slightly when I bump up to 33’s here shortly

 

[Rob5589]

There is a difference, but only for highway mileage.

Bring your speed down to 65-75 and you should see 22+ mpg with 3.21. However, literally YMMV. I see you have the ORG. The 1 inch lift may be hurting your aero/drag.

I have seen 21+ at a steady 68 with cruise. But for me personally, nearly 20 mpg in this pick up at 80 mph (speed limit outside CA) with the bed loaded down with gear is perfectly acceptable. Bests my old Silverado by nearly 5 mpg.

 

[2wd]

I have seen 21+ at a steady 68 with cruise. But for me personally, nearly 20 mpg in this pick up at 80 mph (speed limit outside CA) with the bed loaded down with gear is perfectly acceptable. Bests my old Silverado by nearly 5 mpg.

Right on sir.

Agreed 20mpg at 80mph for a V8 pickup is impressive.

I came from a F150 5.0 which loved, but never got better than 21 in optimal conditions. Now you increase displacement in this Ram to 5.7 and somehow I'm getting 22-24 HWY consistently.

I attribute it to better aero/drag, 8 Sod vs 6 spd trans, and maybe the MDS????

Either way I am satisfied with the MPG particularly for an old school V8 design.

 

[Ram1500OwnerMaybe]

Thanks for the replies.
Lots of good points especially about the RPMs especially with daily hwy driving.

 

[Willwork4truck]

Its way more the driver and conditions. Sure given a test track at a steady speed the 3.21 should get a bit better. Who drives only on a test track at a steady speed?

So buy the truck you want, the gearing is secondary.

 

[RangerZ]

Some of you guys get some amazing MPG. I haven’t seen any of that yet in mine lol

 

[Bigtone]

Did your 2010 have cylinder deactivation?

Yes, it did deactivate cylinders. One thing, forgot about the grill shutters the 2014 had. But other than that and the 8 spd trans, they were identical. i really attribute the approx 3 mpg difference to the gearing. Now, that's measured tank to tank on a 1k mile trip, so it basically is all interstate. I'm sure around town the difference would be less.

 

[rlc2020]

The 3.92 will have more wear and tear, worse gas mileage, and more noise and vibration in the cab at highway speeds.

Oliver392 hit the nail on the head. My buddy has the same truck with 3.92, I have 3.21. off the line there is barely a difference. The 8sp trans makes the gear ratio much less of a factor since there is always a good gear to go to.
My biggest reason for getting the 3.21 was longevity. No matter what anyone says, 500 revolutions per minute more adds up to alot more spinning of parts over the truck's lifetime. I see no reason to have your engine turning 2k instead of 1500 while driving down the highway. I only tow a medium sized boat and only do it occasionally, but I've never had an issue with power with the 3.21's.

Unless you are towing a significant amount of weight a significant amount of the time, there is no reason to get the 3.92 unless you are planning on drag racing everyone.
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