Estimated MPG for Ford F350 Diesel w/373 rear end

[ANewCreation]

Hello everyone, I have a question. I am looking to buy a 2015 Ford F-350 Power-stroke with a 373 rear end and would like to know the estimated MPG difference between it and a 2015 F-350 Diesel with a 331 rear end? Trying to decide which rear end to get. Either is more than enough to tow my TT. Please base your estimate on normal highway driving while NOT towing anything. Thanks a bunch.

[wintersun]

There is not going to be a measurable difference in fuel economy but there will be a difference in towing performance with the taller gears. I never saw a difference with tow vehicles with 4-speed transmissions and now trucks have 6-speed transmissions with two overdrive gears.

It is actually silly to be even talking about MPG with a 1-ton diesel truck. The biggest single factor driving MPG is the person behind the wheel. Fleet operators know that with the same rig one driver will average 6 MPG and another will average 8 MPG or 33% more miles per gallon over the course of a year of driving.

My truck with 3.73 gears averages 14.5 MPG but gets up to 20 MPG on the open road with nothing in tow. With a heavy load and the air drag from a trailer the MPG drops to 12-13 MPG and with a 15 MPH headwind I am lucky to get 10 MPG. At 60 MPH the engine is at 1600 RPM and at the peak torque point for the engine.

Vehicles with taller gearing score higher on the EPA tests and that is all the manufacturers care about with their highly profitable trucks that are also the least fuel efficient. Anyone who still thinks that the EPA numbers are likely to be achieved in the real world needs to do a reality check.

[The_Mad_Norsky]

Please take notice of GoPackGo's speeds he posted.

Between 55 - 60 MPH.

I just traded in my 2011 F 350 dually w/6.7L diesel and 3:73 rear axle.

At those same speeds with that truck, I also could get 20 MPG, but only on those rare occasions here in the northern great plains when the wind was NOT blowing.

Usually in the 18 plus range at those speeds.

[v10superduty]

The mileage difference will be minimal and not worth worrying about.
A carefull driver could probably get as good or better with the 3:73.

More importantly, I bet the 3:73 is rated to tow 2000lbs more.
That may be valuable to you at some time if you upgrade trailer

[Lessmore]

GoPackGo wrote:
I have a 2013 F350 4x4 Long bed crew cab dually diesel with 3.73 gears and I pull a 14,000 pound 5th wheel. I turn about 1600-1700 rpm at 58 mph in 6th gear, which is the speed that I tow most of the time.

Max torque comes in at 1600 RPM.

I believe both 5th and 6th gears of the trans are OD.

In terms of a tow vehicle, there is absolutely no way I would want 3.31 gears in my truck. Just my .02 opinion.

I full time and towed about 6,700 miles this year and another 3,500 'tourist' non-towing miles. I get 11-12 towing and I can get 20-22 mpg at 55-60 mph non-towing. 14-15 around town with lots of cold starts and short trips.

Tim

20-22 MPG solo with a F 350 diesel. That is very good fuel efficiency, with that much size, weight and displacement.

[Slick_Rick]

2015 F350 Lariat PSD SRW 3.55 rear: 16.7 mpg for the first 3500 miles (no towing).

[ANewCreation]

Thank you to all who responded. Your info really helps. I believe you can get the 373 in the 2015 SRW F350 diesel as I have seen a few of them on the Ford dealership's lot and it is in the Ford brochure. I will double check again though since I want a SRW. Thanks again!

[calewjohnson]

I have a 2015 DRW with 4.30 gears...I get about 15 not towing, 10-11 around town, and 9-10 towing.

I have 5k miles on mine.

Cale

[Quahog]

I only got this truck this past Monday and have 300 miles on it. But according to the trip computer, I'm getting around 16 mpg so far and I am currently at half a tank. That's a mix of city and freeway driving. 2015 F350 DRW 3.73 CC LB

[GoPackGo]

I have a 2013 F350 4x4 Long bed crew cab dually diesel with 3.73 gears and I pull a 14,000 pound 5th wheel. I turn about 1600-1700 rpm at 58 mph in 6th gear, which is the speed that I tow most of the time.

Max torque comes in at 1600 RPM.

I believe both 5th and 6th gears of the trans are OD.

In terms of a tow vehicle, there is absolutely no way I would want 3.31 gears in my truck. Just my .02 opinion.

I full time and towed about 6,700 miles this year and another 3,500 'tourist' non-towing miles. I get 11-12 towing and I can get 20-22 mpg at 55-60 mph non-towing. 14-15 around town with lots of cold starts and short trips.

Tim

[shelbyj]

Didn't think you could get 3.73 gears in a SRW F-350.

[Travlingman]

3.73 gearing is only available with a DRW. The 3.31 is with a SRW. Do you want a dually or a single rear wheel, or undecided? With my 2012 dually I get around 16 in town and 17-18 on highway.

[mclaned1]

I have a 2014 f350 with that gearing and get 16.5 city and 18 hwy. I am easy on the gas pedal and use cruise control as much as possible.

[Artum_Snowbird]

It's really the power the engine needs to produce to go down the road. You can produce that power with fuel intake at either a slower RPM or a bit faster one.

The difference comes when you are using the power in a gear range. Assuming you reach your top gear at highway speeds, if you have shifted into high well before you got to highway speed, you will likely stay in high when a hill comes in front of you. If you live in flat land, go with the lower ratio, but if you want to not have your tranny shifting up and down, go with the higher one.

[Taco]

I really doubt there would be much difference.

[agesilaus]

On my 2012 I get 16 or so in mixed driving and 17-19 on highway. Tires make a difference I've found. I swapped to some semi-offroad tires and the mileage dropped by at least 1 mpg, maybe more. Changing to Goodrich All-Terrain T/A brought it back up. Strictly highway tires would probably help more. I have a 4WD which might shave a little off the mpg. Wheels are 18 inch.

I've seen people saying that the rear end doesn't make as much of a difference on these newer trucks because of the 6 speed transmissions. I don't know enough about this to agree or disagree with that.