What size are your tires?

Are your tires that or a 265/70/17?

I have been putting together numbers for tires/rpms and mpgs. Thanks guys!

 

Sorry no they are actually 265/70/17
Good year duratracs.

285/70/17 I had before I would lose close to 1 mpg, nitto crossteks

 

This puts your sweet spot +/- 1600 rpms @ 60 mph.
I had similar results going from the stock 245(31.5) to my current 32.7", 285/70/17. Another friend of mine did the same thing. It is surprising that going up an inch or so has such an impact on mpg but it happens, and you are in turn reducing your rpms by roughly 50.

 

With stock tires, 4.30 gears I've made several 500 mile trips (each way) to San Diego carrying only two kayaks and gear, which is negligible weight for an F-350. About 300 miles of each trip is flat interstate at 75+ MPH, then I climb a 4,500 foot pass and for the duration of the trip I'm in cities and traffic at 60 - 70 MPH.

14 MPG, pretty consistent. One trip I throttled back and set the cruise to 65 the whole way, only saw 15 MPG. Those numbers measured the old fashioned way - miles traveled divided by gallons put in tank. The factory speedo and odometer is a bit off according to my GPS, but it's the reference point I use.

-Joe

 

I just picked up my 2015 F-350 fx4 crew 6.75 bed 275/70/18 on my way up to the cabin. 270 miles each way

I got 14.5 with the cruise at 70 99% of the trip.. only nailed it a few times to pass some idiots.

I had a raptor 700 in the bed a small tool box and rosco riding shotgun.

 

3.73gears I assume?

 

Yes 3.73's hit 18000 on the trip.

 

Nice. These reports are the reason I ordered 3.73s on my 2017

 

And why I ordered 4.30's on my '17. There doesn't seem to be a concrete difference in them. Maybe at 70+mph unloaded and running 31.5" tires the 3.73 will out preform regularly.
It also depends on what tires a guy wants to run or how much town driving. It is safe to say that the 4.30's with the taller 34" tires and/or town driving will net better mpgs.

 

Without knowing what the new transmission will deliver, I'm sticking with my 3.73 order and hoping the G-transmission adds some low end TQ while giving me the best mpg performance running empty. Yes, I'll be turning the 20" wheels. No I don't think I'll notice a dang bit of difference.

After all, if I wanted to brag about mpg, I wouldn't buy a SD truck.

 

Yeah I hear ya. I have "ask an engineer" several times about the new G gear ratios. It is really frustrating that it is not posted anywhere. The only info I have ever seen stated the new G has a lower first gear for take off and is designed to give a significant bump in fuel economy.

 

Just did first trip in 2015 F350, 6.2, FWD, crew cab, 8 Ft box, 355 gears I believe.
Only using the dash indictor which showed 17-20 MPG converted from 14-15 L/100KM as this is a Canadian truck and imperial gallons is our standard. 30% Mountain driving , 70% flatland at 75-80 mph. truck is basically new with 1200 km (700 miles) at start of 2000 KM trip.

 

I thought I would post my first mileage numbers since taking delivery of my new truck this past Monday, May 23rd. As you can see in my signature, I have the F250 with the 6.2 gas engine and 4.30 year end.
I knew I was going to give up some mileage because of the rear end on the highway but I was pleasantly surprise by the numbers on my first two fill ups.

When I picked the truck up, it had 25 miles on it and the computer mileage was showing 8.7 mpg's. I choked a little at that but it steadily went up as I went through my first tank. The first photo below shows my mileage numbers per the computer when I pulled in to full up after burning the first tank. Remember, I did not know how full the dealer filled the tank so the while it read full when I picked it up, I was not completely sure if they topped it off or quit putting fuel in the first time the pump shut off automatically.

Miles Driven - 300.4
Gallons to fill up - 25.46
MPG hand calculated - 11.80
MPG on computer - 12.1
This was both city and highway driving. Highway was at 60 mph and the tach was reading about 1750 rpms and I have the 275/70/R18 stock AT tires on mine that come with the FX4 package.




We then took a trip which we drove in both mountainous and hilly terrain here in Wyoming. I filled up on our way back after driving 191.1 miles. Below were the statistics.

Miles Driven - 191.1
Gallons to fill up - 12.837
MPG hand calculated - 14.89
MPG on computer 14.1
This trip was mainly high driving at 65 mph and the tach was reading about 1950 rpm's. Up some of the hills I would drop from 6th down to 5th to hold at 65 mph and on a few it dropped down to 4th gear. This was running empty with just my wife and probably 200 pounds of gear in the bed.

The picture below was after we got back to town. I snapped a photo of the trip meter that I reset when I filled up. It shows we went 143 miles, used 8.30 gallons of fuel and got 16 mpg according to the computer.




After reading a lot of negativity about how the mileages on these Super Duty's with the 6.2 gas engines and 4.30 rear ends are so bad, I am hear to tell you after putting the first 634.5 miles on my truck that I am very satisfied with the miles I have gotten so far. I am not a lead foot and I know that there will be conditions where I will get less than desirable fuel mileage (driving on the 80 mph interstates back here, winter driving, pulling the heavy trailers, pulling in wind etc.) but over all, I could not be happier.

I had been driving a Toyota Tundra for the past 6 years with the 5.7 gas engine in a 4x4 Double Cab. I can tell you that with 80,000 miles on it when I traded it on this Super Duty, I was getting no better mileage with it and it is a half ton truck.

So, I can only speak from my personal experience over the course of the first two fill ups and I am telling you I am very satisfied with my mileage. I can only imagine as it gets more broken in and loosens up, it will gain some over what I am getting today.

 

That is great. It will only improve too! I have been tracking mpg info since I realized my 3.73's and 33" tires were a towing let down. It seems that unless one is running the little stock 31.5" tires, the 4.30 will get the same and usually better mpgs in many driving conditions. The only situation I don't have a lot of info on is 70+ mph empty interstate driving. Tire size plays a roll here too.
I think it is difficult for many to understand how the 4.30's simply don't get worse mpgs. I know a year ago I would have assumed the same. I was so used to diesel trucks making so much torque down low, that gearing is not nearly as important. But today with the double overdrive 6spd, and the 6.2 gas motor, the lower gears just seem to work much better.
My truck on the hwy gets better mpgs in 5th running 1750 rpms than it does in 6th at 1450 rpms. I just don't think the 6.2 makes enough power around 1500 rpms to efficiently keep this big truck going down the hwy. I have been experimenting with this scenario for months on my drive to work to simulate my future gearing.
I drive my truck easy, and drive roughly 50/50 town/hwy(55mph) and my calculated fill ups are consistently in the 11-11.5 range.
I'm really looking forward to my new 6.2 coming with 4.30's.

 

I have experimented with driving with 6th gear on and off. Does not seem to affect mileage at all.