3.31 vs 3.73 Highway MPG Difference

[TacoJon]

Another day of driving and nearing the end of break-in period. As you might imagine, I get more pull at lower RPM but it falls off at higher RPM where the 3.31 pulled better. Noticing less jerky shifting and better overall shifting too. Hopped on the interstate last night for about 8 miles. I usually got around 21 or 22 with my old gears and I got around 20. Cruising RPMs at 75 mph have gone from around 1500 to around 1700.

Not a fan of the digital screens. The refresh rate isn't the best and you can tell the tachometer is a little laggy with what the actual engine is doing. I would rather just have analog gauges.

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[JCsTruck]

Another day of driving and nearing the end of break-in period. As you might imagine, I get more pull at lower RPM but it falls off at higher RPM where the 3.31 pulled better. Noticing less jerky shifting and better overall shifting too. Hopped on the interstate last night for about 8 miles. I usually got around 21 or 22 with my old gears and I got around 20. Cruising RPMs at 75 mph have gone from around 1500 to around 1700.

Not a fan of the digital screens. The refresh rate isn't the best and you can tell the tachometer is a little laggy with what the actual engine is doing. I would rather just have analog gauges.

This is great information. Thank you.

 

[sporkfed]

The

Not a fan of the digital screens. The refresh rate isn't the best and you can tell the tachometer is a little laggy with what the actual engine is doing. I would rather just have analog gauges.

These days, all tachs, whether a needle gauge or digital, get their engine speed data from digital crank speed sensors that run at a finite sampling rate. So unless your digital display is bugged, they should have the same latency. And both types of gauges can easily keep up with the acceleration of the rotating parts.

So, all of this is to say that, if you are seeing something laggy, then maybe they have a software algorithm that collects RPMs over a finite amount of time, like 0.1 sec or something, before updating it, to prevent it from fluctuating around too much and causing people to freak out. And quite possibly this update time is programmable with Forscan.

 

[Aliass24]

My 24” with the 5.0 leveled with nitto 315/70/17’s averages 16 hand calculated on winter fuel and 3.73’s

 

[Larrymoe]

My 24 RCSB gets under the sticker MPG. About 15-16 in town. Only hits 20 on the highway with the wind behind me going no more than 60.

And that's actual MPG, not what the truck says. That's off 2-3 MPG.

 

[TacoJon]

My 24 RCSB gets under the sticker MPG. About 15-16 in town. Only hits 20 on the highway with the wind behind me going no more than 60.

And that's actual MPG, not what the truck says. That's off 2-3 MPG.

Yeah, the rated 24 mpg these things have on the sticker is crazy. I am getting around 18 or so on the highway. Since I regeared I lost 1 or 2 highway MPG. In town I am now getting around 13 mpg. I live in a small town so I idle a fair bit and my trips are short with lots of stop and go, so 13 mpg is to be expected. If I lived in a big metro city with long stretches of 45 mph drives and longer distances I know I would get better.

 

[ThumperF150]

Another data point that someone might find interesting.

24 RSCB 4X4 5.0 3.73s

99.9999% of my driving in this truck is less than 5 mile trips with no freeway. So I let it warm up a good minute or two before I drive away (0 mpg while doing so).

13ish mpg stock.

10ish mpg after I added 35” tires and of course it felt slightly slower.

13ish mpg after I then added 4.11 gears and correct speedo error with a Hypertech in line module.

A short run on the freeway showed 1550-1600 rpms at 60 mph and roughly 1700-1800 rpms at 70 mph.

At 60 mph it looks to be getting 25+ mpg but who drives 60 on the freeway?

 

[GODZILLA]

Apologies if this has been covered, but I didn't read every post.

Folks need to keep in mind that the "advertised" MPGs on the sticker are calculated at highway (NOT interstate) speeds in ideal conditions. That means it's a no wind, flat ground, stock tires, truck with no lift or level and not exceeding 60-65 MPH. You're never going to see those numbers running down the interstate with speed limits of 75-80 MPH.

It also should be noted that anyone running larger tires than stock isn't getting accurate speed or MPG calculations unless they've recalibrated their speedometer to account for the circumference increase of the tires. For easy math, say you increase your circumference by 10%, then you are going 1.1 miles for every mile the odometer reads and that changes the MPG calculations.

My real world info on the topic: Truck is bone stock, has the 3.73 axle. On a long road trip I checked several tanks. My dash said I got between 0.8-0.9 MPGs more than hand calculated. So rather than getting 21.8 MPG I was at 20.9-20.0 with everything from slow town pass throughs to I-15 stretches set at 77-81 MPH on the cruise. Add to that the fact that there were multiple stops spent idling while myself or somebody else on the trip went in to pee or buy snacks, and I can say I'm easily pleased with the fuel economy for a truck.

 

[Jean Deaux]

My 24 RCSB gets under the sticker MPG. About 15-16 in town. Only hits 20 on the highway with the wind behind me going no more than 60.

And that's actual MPG, not what the truck says. That's off 2-3 MPG.

Exactly the same for my 2021 RCSB FX4, 3.31.
My regular drives are about 5-6 miles daily, 90% in town with 30mph speed limit. Before replacing active dam with Tremor front end and on OEM Pirelli Scorpions 265/70R17 my average was 16-17 in town and 20-21 on highways. Active dam delete and Tremor kit didn't affect the average mileage but my new Toyo Open Country A/T III shoes did. I lost about 1 mpg in town and at least 2 mpg on highways.

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