Could it be that the 4.30 gears help push through the air wall (less engine load) at higher speeds than a truck with the 3.73 gears? Or it may be that you have one of those trucks in which everything came together just right in manufacturing. Either way, congratulations on such a great truck!

 

The 4.30 gears = better mpg's almost all the time for most SD drivers.

 

My assumption for the extra downshifting at higher speeds is wind resistance. There's not enough difference in the power out put at the rpms of 70 vs 80 mph to make up for the wind resistance of a big brick at those speeds. Anyone that's ever rode a motorcycle at those speeds without a windsheild can testify to the difference in 10 mph. 60 isn't to bad, 70 starts getting loud and you can really feel it. 80, you better hold on and keep your head tucked or your helmet will try to rip your head off backwards, 90+ you better keep your body tucked because it gets violent.

The difference in mpg when pulling an inclosed trailer/camper at 60 vs 70 is huge.

 

Very good point!

 

I've seen you advocate for the 4.30 gears frequently. We live in a relatively equal geographic location. I towed my 6.5k trailer through the Columbia River Gorge a few weeks ago and averaged above 9mpg. My question is if 4.30 was the best ratio for Super Duty trucks, why do the engineers continue to use the 3.73 as the base gear set? I would be curious to see a true scientific comparison. With my 3.73's, I get 11.5 in stop and go traffic through a full tank. Highway I get 14.2.

 

I think raindesert and I have a very similar view on the gears. My '16 ccsb 4x4 3.73's has the small 31" tires. My best mpg in perfect conditions was 17mpg. That was empty. That's a very good number for these trucks. But that's the only configuration that is going to net better mpgs. My dad has a '16 rc 4x4 with 4.30's( I convinced him to change his order to 4.30's) and the same wheel/tire combo. His is a regular cab, BUT, the bed is loaded down with tools, and mine is empty. Probably very close in weight. The first week he had the truck, before it was broke in, he was neting 2mpg better daily, in the same driving conditions and we have very similar driving habits.

With larger tires(aftermarket or factory), around town, or towing, the 4.30's always do equal to or better on fuel mileage. The rear end is the final torque multiplier and you can't adjust it by locking out 6th gear with 3.73's to get a similar driving experience as some think. I've not had the chance to tow heavy with dads truck, but can't wait.

But I will say with my little tires, towing with 3.73s is not nearly as bad as some have made it out to be. 8500 pounds 600 miles one way across the smokies neted me 9.5 mpg. I kept 6th locked out most of the trip, and hit 3rd gear on multiple occasions. I can't say the truck struggled at all, it held its speed no problem, but I think 4.30's would have pulled 6th gear easily, and the only place that would have seen 3rd would have been black mountain on i40.

 

I follow as many mpg reports as possible. I have always done that with my SD's because I like to. There seems to be no disadvantage to a 4.30 and only things to gain. And it is a fact, towing with a lower gear nets better mpgs in NA trucks like the 6.2.
Tire size is a key factor in this. The stock 31.5" net nearly the same hwy rpm as a 34.2" stock tire with 4.30's.
I believe the default gearset is 3.73 because in general when people hear 4.30 they simply assume bad mpgs. That is the case 100% at my dealer. I had to show them rpm calculations across tire sizes for them to realize w/the 6spd tranny and the .67 overdrive the 4.30's work well.
I won't have an exact apples to apples comparison because my new truck coming soon has the updated motor, new 6R100 tranny and 4.30's.
11.5/14.2 seem pretty avg numbers, I'm usually 11 for a tank avg which includes lots of rural back roads. I have run my 60mph stretch of hwy with 6th locked out vs not, everytime I netted about 1mpg better in 5th. That's the best comparison I can do for my truck. I run 33.2" tires.

 

I know we've discussed this a bit before because my experience is not the same. With 3.73's and 295/60/20's at 55-60mph on my stretch of highway to town(about 12miles) if I lockout sixth like I almost always do, I get worse mileage then if I allow it. I don't track it closely because I'm not all that concerned with 1/2mpg in mileage or whatever but it's significant enough to the computer on my truck that when/if I allow sixth gear on that highway run my 'miles to empty' goes up while I'm driving.

As I said. I don't really care about 1/2 or a whole mpg myself, but just what I've experienced. I'm dying to put 4.3's in just for the extra oomph as I pull a three horse bumper pull more than I drive empty.

To clarify my little sixth gear experiment is done empty. Pulling the trailer I never allow sixth right up to 75mph, as it's a useless gear while towing in my configuration.

 

Hey Squisher, I wonder if your tuning and mods make some of the difference you may have with others? I know you have tuning and exhaust mods, I have always been interested in playing with the exhaust system.

 

You may not believe this, but I've seen a 1 mpg increase on the freeway after replacing my steering stabilizer. I replaced the OEM with a Ranch RS7415 because I was not happy with the steering wander when going through construction shoulder diversions pulling my 5th wheel. The Rancho stabilizer eliminated the problem. Right after I changed it, I took an hour drive on the freeway and noticed the lie o meter was showing the 1 mpg increase. I was chalking it up to a tailwind and didn't give it much attention. I spent 30 minutes at my destination and returned home. I noticed the same 1 mpg increase on the way back. I disregarded the stabilizer as any possible reason for the improvement. It still had me wondering, so I did some Google research and found that motorcycle front stabilizers apparently increase their fuel economy substantially. Has anyone else noticed a difference in fuel mileage after replacing their damper.

 

I've got a 2016 F250 4X4 with 3.73 gears. I have not pulled my 31' Holiday Rambler 5th wheel yet with it, I use my '96 F350 dully with a 7.3L for that, until the day comes I need the F250 to pull it. I do pull my boat which weighs roughly 3800lbs. Fuel consumption about 11-12 mpg. Everyday driving around town 13-14mpg. I just drove round trip from South Mississippi to San Antonio TX with an average speed of 80mph (not towing) and got 15mpg.
I've had this truck since April and traded in a 2011 150 for it and have not regretted it one time.

 

2015 truck in my sig. 28,700 miles been tracking since day one on an excel spreadsheet.
Combo tow,daily drive 10.19 mpg, Lie-o-meter avg 11.5.
When I tow it will drop to 8 or so.

 

I just got back from a camping trip where I pulled my ATV on a 14 foot trailer that also had 3 full coolers on the trailer. The bed of my truck was also full of gear.
On my trip to camping I got 11.2 mpg and I had a head wind of about 10 mph and was gradually going up in elevation from 5200 ft to over 9000 where we camped.
On the way home I did not have a headwind at all and I got 12.8 mpg.
My ATV trailer has a back loading ramp gate on it that is 4 feet tall and looks like those old BBQ grill grates. Anyway, it acts like a parachute.
I just turned 3000 miles on the odometer when we got back to town.
I am pleased with the mileages I have gotten since getting the truck in May.

 

My hwy mileage really improved around 3500-4000 miles. Luckily, right before I went on my big trip.

 

Just completed a trip from NE Pennsylvania to Rapid City, SD towing a 2015 Forest River Wildcat 327CK fifth wheel. The fifth wheel weighs around 12k when loaded. I tow with a 2012 F250 Super Cab Lariat 6.2 equipped with 4.30 gears. The only upgrade I have done to the truck was to add 2 helper (overload) springs.


The route I took was SR 414, SR 15, SR 220, I80, I29, I90 for a total of 1627 miles. My MPG, according to the on board computer, was an average 8.5 MPG.


I use cruise control all the time, the truck was in 6th gear 98% of the trip. On steep grades, the truck dropped into 4th gear and seldom into 3rd gear. I would estimate the lowest MPG was experienced from Mitchell, SD to Rapid City, SD.