How are the 2017 diesel F450s doing fuel mileage wise? Thank you. Strongly considering a new F450

 

Don't buy it if you want decent unladen fuel mileage.

Unloaded 90 percent highway I am averaging 12.4.

Speed is usually 75mph.

If if you can keep it under 60 you will average 14+.

do buy it if you want the most bad *** truck on the road. It was a sacrifice I gladly took.

 

How many rpms are you turning at 70 and 75?

 

The F450 will spin at 2000 RPMs at 65 MPH in 6th, so 2150 at 70 and 2300 at 75.

 

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Thank you. It will be hooked to a trailer probably 80% of the time. Any yes closer to 70-75mph.

 

Thank you. Is that posted somewhere or did you do the math? If the later, could you tell me what those rpms would be with a 2in taller tire?

Would they be about 6% less (2in taller tire / ~32 in tall stock tire = ~6%).

 

Initially the math (using the loaded rev/mile from the tire manufacturer, not unloaded tire diameter), then confirmed via test drives.

When increasing tire size, you decrease the RPMs by the same ratio as the loaded diameter change. The difference will be about the same as the unloaded diameter changes.

Specifically, for a 2" change, (31.9" --> 33.9")
65: 2000 --> 1882
70: 2153 --> 2026
75: 2307 --> 2171

If you tow large/heavy up long large hills (6%-7%), I suggest you consider what RPMs you will spin in 5th and 4th gear at the speeds you want to pull. The speed just over the point when the truck will upshift will be your worst power point. The stock setup on the F450 pulls at max HP (2800 RPM) at these speeds:
5th: 71 MPH
4th: 53 MPH

Watching the youtube videos of the trucks towing up big hills, it looks like the transmission will upshift just over these speeds (maybe 2900 RPMs or so).

If you bump up the tire size 2", your strongest pulling speeds will be:
5th: 75 MPH
4th: 56 MPH

If you plan to tow up mountains at 70 MPH, the stock tires will do better. If plan to tow up mountains at 75 MPH, the taller tires will do better. If you don't pull hills heavy, it doesn't really matter.

 

good stuff right there thank!

 

Thank you, I appreciate all the info. So my the RPMs do drop about +/- the 6% for the 2in taller tire.


I don't plan on hauling heavy on extended high grades, so that shouldn't be an issue for me.


I plan on installing 265/70/19.5 on 6.75in wide wheels when I get my new truck. Outers from American Force, rear inners and the tires from Rickson. Primary reason is aesthetically to fill up the wheel wheels and to have a better all season tire compared to the HSRs, hoping that the slight reduction in engine rpms due to larger overall diameter helps with the MPGs slightly, but at best it might just compensate for having the wider tires on the ground.

 

Great analysis 2009kr. Thanks for that.

As you already know, it seems we are both waiting for similar 450's. My primary application for the new truck is pulling a 17 - 19K toy hauler. We are in Colorado and it seems almost every trip involves quite a bit of hauling on a grade. Sometimes, long, steep grades (e.g. Vail Pass, Wolf Creek Pass, Monarch Pass, etc.) That said, we make some long flat runs across the big western states all the time. Even on the flats, I've become quite comfortable settling in between 65 - 70.

I'm trying to settle on the wheel / tire combination that will best fit this application and, hopefully, provide acceptable winter weather performance when the truck is empty.

I'd be very interested in your thoughts. I know the HSR's don't have the best all-weather reputation, but I keep coming back to them being a good, if not the best, compromise for all around hauling.

 

I'm getting 14.3-14.5 average driving with plenty of city driving.

I get 15 mpg when on long highways.

All unladen as I just put 1000 miles. I don't know yet what I'll get towing.

 

What drew you to the 450 if your immediately going to change the wheels and tires and are concerned about mpg? For less money you could've gone with a 350 and had 1500 less tow rating but more payload.

Hope I'm not coming off like a dick, just curious why you went this way? I know the wide track axle has its benefits but I don't think it would justify atleast 4K for that and some larger brakes. Again, it's your truck but I'm just curious

Brett

 

Valid questions, The reality is that whatever truck I ended up with (F350 SRW, etc) it is likely that I would have swaped out the wheels and tires, it's one of the ways I make my vehicles my own and perhaps just slightly different that anyone else's. Moving to a slightly larger tire fills out the wheel wells just a bit more and that is a look that I prefer.

I wanted the 450 for the wide track front end, if that option was available on the 350, it's likely I would have gone that route. And while fuel economy isn't my primary concern, I thought I would post on this since it was a thread specifically related to the vehicle I will soon have and I was curious what the overall increase in tire diameter would have on hwy RPMs.

 

I gotcha. Looking forward to yours coming in and seeing it with the new wheels and tires. Mines supposed to be delivered on Jan 14 but we will see

Brett

 

Thanks and Good Luck! I'm just ahead of you. Mine was built 12/17 and the ETA is 1/1. Fingers crossed that it all goes as planned from here on out.