Horrible fuel mileage

[Seehorse]

Ok guys, I've a 2008 F450 with roughly 20k miles on it... I'm getting less than 10 mpg bobtail and between 5 - 6 mpg pulling 17,000lb of trailer. What the heck is wrong with this thing????

That's about 2/3 the mileage that 18 wheelers are getting, and it's HALF the mileage that Chevy 2 1/2 ton trucks pulling equivalent trailers get. It's currently in the dealership AGAIN to get the mileage problem fixed. What can I tell them to do to bring it up to where it belongs? If the Chevy C65 is getting 12-14 pulling 18k of trailer then there's no reason for the Ford 450 not to do the same.

As a comparison when I bought the truck new I traded in an 05 F350 diesel that got 17 mpg bobtail and 10 - 12 mpg pulling the same trailer. I'll tell you, something's gonna change drastically or that's the last Ford truck I'll own. I've gone thru 4 previous diesel Ford F350's, a '95, 99, 01 and 04 and been happy with them. Every one of my previous trucks got decent mileage.

 

[ponyexpress94]

Does this truck has the High Capacity Trailer Towing Package? The 6.4's are not as efficient on fuel as a 6.0 and nowhere near a 7.3. If the dealer reflashes your PCM and things don't improve about the only two options I see are installing a DPF delete kit with a tuner (this will VOID your warranty) and/or possibly installing a Gear Vendors Overdrive kit to drop your revs on the highway. If neither of these options suits your taste the only other option is to adjust your highway speeds downward to achieve slightly better numbers. My experience is any speed over 70 mph destroys any chance of good fuel economy unless the truck is geared really long (numerically lower). Sorry to hear that you are unhappy, but you still have a great truck.

 

[Seehorse]

I'm not sure what package it has, but I will say that if the dealer can't get the mileage with trailer up above 10mpg then the truck's gone. Yeah, it drives nicely and pulls adequately, probably slightly better than the 05 diesel that had the 18k tow capacity... but it's getting half the mileage the 05 got.

I've put up with it for over a year now and over 20k miles... my last cross country trip brought it home when I was talking to a trucker filling his Kenworth at the next pump. He was getting 8 mpg with a loaded rig to my 6 mpg.

I really hate trading in the truck since I'll take a bath on it, but it's costing me a ton in fuel. Voiding the warranty worries me since our 05 had 3 major breakdowns on the road. The difference in the mileage of the 08 has used over 8,000 gallons for what the 05 would have done with 4,200 gallons. That's getting pretty expensive.

 

[ponyexpress94]

I don't think it's possible to get 10+ mpg on a 6.4Liter F-450 pulling a 18,000 lb. trailer.

If you take a look at the vehicle ID sticker on the door frame when the drivers door is open look for the "AXLE" section. What is the code in that section of the sticker? If the code is 8L you have 4.88 rear gears and therefore the High Capacity Trailer Towing Package. With this gear set the truck can pull 24,000 lb. trailers but somethings gotta give and it's gonna be the fuel economy. If your axle code says 4L then you have the 4.30 rear gears and depending on when your truck was built will determine how much it can pull. Early production trucks were rated to pull 20,000 lb trailers while later trucks were rated to pull 24,000 lb trailers as the 4.88 gears were discontinued because SUPRISE the 4.88 equipped trucks had horrible fuel economy.

Granted this info doesn't solve your problem but it at least arms you with some information. What speed are you driving the truck with the trailer on the highway? Are you using the onboard computer's fuel economy numbers or are you hand calculating them? In some cases the onboard computer has been known to be off by as much as 2 to 3 mpg.

Your second post states your 05 dually had the "Tow Boss" package so it had the 4.30 rear gears. If your 08 has the 4.88 gears and I'm betting it does then it's not even a fair comparison of trucks especially when you factor in the 6.4 being saddled with all the emissions stuff that further chokes the engine and also burns fuel every time it goes into regeneration mode. Since you don't want to void the warranty, I would seriously consider the Gear Vendors Overdrive unit. I have read about a few people that have had good sucess on the 6.4 Liter F-450 increasing their fuel economy by lowering the engine revs when the truck isn't excessively loaded. Additionally, the Gear Vendors unit will probably cost less than half of the depriciation that you will realize if you sell the truck.

Good Luck

 

[Seehorse]

On the speed, I typically run roughly 70-75 cross country, that being the speed limit much of the way. All the mpg is based on the onboard computer, but it's getting roughly 200 miles down the road on a full tank, around 35 gallons. My back of the envelope figures put that at between 5-6 mpg. Of course, it varies with the terrain, on the flat vs in the hills. A typical trip will be anywhere from 400 - 1,800 miles driven; I own a Video Production Company and we do shows from New York State to Arizona. The last trip was from Phoenix, Arizona to home base just north of Indianapolis... the computer says an average of 6.1 mpg for the whole trip. (I reset it when we left Phoenix)

I don't have the truck handy at the moment, I dropped it off at the dealership this morning so I can't look up the axle info. I do know that at some places in the mountains the 05 would drop to about 40 mph, particularly in a long uphill portion on I-17 from Flagstaff to Phoenix. The 450 is a little better, dropping to around 50 mph in that same area.

We had the recall computer flash done in January, since then it's been popping that damned "cleaning exhaust filter" message probably about 20 out of every 100 miles driven. It may have done that before, but it didn't show up on the dash prior to the update.

I will investigate the Gear Vendors unit you mention, I assume a web search will find it?

 

[ponyexpress94]

Below is a link to the Ford Automatics section of Gear Vendors web page.


http://http://www.gearvendors.com/f2wd4s.html

I'm not sure why they don't have 4wd trucks listed especially since both trucks I have seen the OD units on were 4wd. Hope this helps give you some alternatives for your problem. Please post back when you decide what you will do.

 

[Seehorse]

Thanks for the info, we'll see what happens after the dealer turns it loose... they've always been great to deal with... I wonder if it has anything to do with buying 4 trucks and 5 cars from them over the years

 

[nascar_fan28]

my neighbor has a dodge 2500 mega cab 4x4, with cummins 6.7 and he gets around 12 empty.. so i think the big three are all having fuel economy problems. i know that would make me mad though, if i bought new truck and it got that low of mileage. Good luck

 

[DaveBen]

Federal Gov't emissions is why all of the trucks mileage sucks.

Dave

 

[93turbo_animal]

yes none of the new trucks are going to get as good as the older trucks for some reason the goverment believes burning 2x's as much fuel is better for the enviroment