TERRIBLE MPG

[cmart264]

So I have had my 2011 6.7 for alittle over a years now and this past weekend really set me off. I drive into upstate New York every weekend. This weekend was the all time topper on ****ty fuel mileage. I was towing a 2 place aluminum snowmobile trailer enclosed probably 2000lbs behind the truck and I was getting 10.8 MPG. Without a trailer on I got 12.5 MPG this is all after my truck was at the dealer for warranty work and I'm now wondering if they reflashed the computer? Only non stock item on my truck is 35" nitto trail grapplers but the mileage wasn't this bad before it saw the dealer!

What do you think?

[Painted Horse]

Head wind, Cold temps, Slushy roads. Combination of all of the above.

How old are your filters? How much idling did you do to warm up the truck. Lots of possible variables.

I have noticed that the weight is not as much a consideration as the wind resistance and rolling resistance of the extra axles. I can go from 18 mpg empty to 12.5 mpg for an empty flat bed trailer at 2000lbs and when I add a 8,000 machine it drops .5 mpg more.

[cmart264]

Winds and temps weren't a big deal during the trip virtually no wind temps were probably close to 15 degrees. Filters were changed at 15,000 miles and truck currently has 25,000 miles on it. Could the filters be an issue already? I'm adding anti gel nearly every tank ful also if that would have any effects.

[ucpa111]

Sounds a bit weird to me. Even with slushy roads, idle time, and head winds I can still pull 16-17 hand calculated out of a tank (assuming 3/4 interstate driving in slushy conditions) - unloaded. It could be the fuel you purchased possibly? It might make sense to call and ask the dealer if they did anything.

[JimNVA]

10-12mpg is crazy talk. I would ask the dealer if they messed with the computer, not that they would say or not, let them know your drop in mpg. Maybe get a free diagnostic, filters,etc out of the conversation. That's all hopeful thinking.

[31 YNOT]

I will say as soon as I hook a trailer to my truck the milage drops off quite a bit. But after that it doesnt really matter how much it weighs I can get 11mpg towing 20K+ or 12mpg towing the trailer empty at 7500 lbs. Winter fuel also hurts my milage though

[dieseldan2005]

My brother is complaining of the exact same thing. He has a 2012 350 crew KR with less than 20k on his. Last weekend he pulled a little haulmark single axle trailer with one sled in it and got 7.5 mpg. He was going 85mph and it was below zero, but that is still extremely low mpg. I keep telling him to slow down, but its how he drives. It doesn't matter what he drives he complains about it. Everything except his excursion. He still gets almost 20mpg in his 04 ex driving the same way.

[Hawkeye Diesel]

Winter Blend Diesel fuel ..... Always lowers my MPG from November until April when they stop selling it at the pumps.

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[Lowbudgetracer]

Well when I first got my truck July 12. I put roughly 300-500 miles on it and drove up to Mich from NC. I got right at 19.5-20 MPG and now it's way down. I have 31000 and make that same trip quit often and it gets between 15-17.5. Running empty, just me and clothes at 75/78 MPH. I've seen a noticable drop around town as well. All filters (fuel/air) got changed at 22000 and there was no water detected. I'm going to take it in and see if there is something wrong. If it checks clean I'm ripping the emissions crap off and giving it a tune as well.

[Cratos]

what rear gears do you have ?
I have 355 and with the 11500 trailer I get 11.5 without I get 16-18mpg