MPG 3.92 compared to 3.21 ?

[klodge741]

I got 5800 getting around 18.5. This is all mix driving city highway. I also noticed once I hit around 3500 the mpg went up. Also about every 1000 I saw a increase.

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[TestPilot57]

That is the best way to answer the post: city only, mixed, or hwy driving.

Actually, I think that's totally meaningless. What "city" etc means to one person is something else entirely to another.

The only meaningful comparison is the same route(s) by the same driver, with different vehicles for long periods of time (I'm thinking minimum 20k, up to 50k depending on the type of driving).

And even then, SOMEONE will say "You claim that your mileage went UP in the 5G while mine went down" wah, wah, wah. Chalk that up to non-scientific methodology on the part of one, the other, or both.

The automakers and EPA spend millions doing fuel mileage testing. While very few people will agree they are "spot on", I can guarantee they are a whole lot better at getting a "good" number than a bunch of backyard fuel mileage engineers.

 

[Elkman]

my 2014 with 3.21 8 speed 4x4 with my 295/65/20 averages 16.8 mpg mixed driving, my 2018 with 3.92 8 speed 4x4 with the exact same tires is averaging 16.4 so far. I can say the 3.92 actually picked up .5 mpg last week when i put the larger tires on? Not sure why but who am I to complain.

I think Im about the perfect example as my commute is within a minute every day its 75% highway 25% city and i can tell someone within a minute of when Ill be at work or home barring an accident. Having an identical setup with level and tires I think Im about the best guinea pig.

Larger tires means you changed the gearing and now have less than 3.92 with your truck. How much less depends on the increase in circumference of the new tires compared to the ones from the factory.

MPG depends a great deal on the skill of the driver. The big rigs average 8 mpg but there are what are known as "10 drivers", the guys and gals who have the skill to get 10 mpg and improve fuel economy by 10-20 percent driving the same rigs over the same routes with the same loads as other drivers.

The easiest way the fleet operators have found to get their drivers to operate more economically is to do route planning. If the truck has a dock reservation for 2 pm then the trip calculator determines how fast they need to arrive on time. If they arrive earlier then they burn more fuel and spend more time sitting outside while waiting to drop their load.

I used to drive at the fastest speed I thought I could get away with and not get a ticket but now I drive at the speed I need to get to my destination on time and no earlier. And if it does not matter when I get somewhere then I drive at 65mm or slower depending on the traffic and type of highway. It is not to save on the cost of fuel which is the least expensive part of owning a car or truck but to reduce stress on myself while driving on what in my area tend to be very busy highways with a large percentage of people that have poor driving skills or are highly aggressive drivers of limited intelligence.

 

[WilliamS]

Larger tires means you changed the gearing and now have less than 3.92 with your truck. How much less depends on the increase in circumference of the new tires compared to the ones from the factory

This is very correct, the overall ratio with the larger tires is now lower and actually lower than a stock tire 3.21. A 35 inch with 3.21 is more exaggerated further to a lower overall ratio. Tire weight plays a larger factor than most expect as well. They assume the larger the tire, the lower ratio, in theory better mileage. The unsprung weight is more substantial than you thing when powering them. That’s why some big rigs can disable and lift those tires off the ground.

 

[Gen3CoupeTX]

I insisted on 3.92 gears, regardless of MPG differences. I've been pleased with mine, just hit 2K miles. About 600 of that was round-trip from Houston to Dallas, cruise set at 79 mph most of the way. The rest of the miles is just local drives. I've not ever reset my MPG number, and pic shows 18.3 average. Old-school calculation comes in at 18 even. I can't complain about that! My prior Ram was an '05 SRT-10 Quad Cab, so this new Hemi / 3.92 combo seems like a gas miser to me.