2016 Ford F-350 Crew Cab LWB Dually 6.7 Mileage

[Texas_Roadrunn1]

Our 6.7 liter truck mileage has dropped from the 14-16 mpg range on the highway to around 12-13 mpg when not towing. Truck has about 35,000 miles on it. We have seen mileage in town as low as 10.5 mpg. We have a K&N air filter which has been recently cleaned and we have added Power Service Diesel Kleen Injector Cleaner and Performance Improver to our last tank of fuel without any improvement. Has anyone had similar experience with the Ford 6.7 liter diesel. If so, what was your resolution? Our dealer doesn't seem to want to confront the issue. Thanks in advance for your help.

[ppine]

I have a big heavy F-350 with the 7.3. It gets 20-23.8 mpg empty.
My uncle Alaska Bob was a diesel mechanic for decades. He taught me the importance of getting air in and out of a diesel engine. After market air intakes (not just a different filter) and a new larger 4 inch exhaust system make a big difference.

The head pipe on my stock exhaust was 3 inch in diameter except there was a 90 degree bend that flattened the pipe. Replacing it with an after market 4 inch pipe that is totally round changed the performance of the truck.

[FishOnOne]

ShinerBock wrote:

Texas Roadrunner wrote:
Our 6.7 liter truck mileage has dropped from the 14-16 mpg range on the highway to around 12-13 mpg when not towing. Truck has about 35,000 miles on it. We have seen mileage in town as low as 10.5 mpg. We have a K&N air filter which has been recently cleaned and we have added Power Service Diesel Kleen Injector Cleaner and Performance Improver to our last tank of fuel without any improvement. Has anyone had similar experience with the Ford 6.7 liter diesel. If so, what was your resolution? Our dealer doesn't seem to want to confront the issue. Thanks in advance for your help.

My brother has a 2012 F350 SRW and his lifetime average is around 13.5 mpg which is inline with most averages on fuelly (LINK). We also live in the San Antonio area as well and he only tows his 10k travel trailer down to Rockport a few times a year. I remember him complaining of his mileage dropping after a few years of owning it as well and I believe it is still the same way.

Although many things decrease your fuel mileage during the winter like winter blends fuel that was already stated and even the cold air itself. Air becomes more dense as it gets colder and if I recall correctly from one of the fuel economy studies at Cummins, aerodynamic drag increases by 2% for every 10F drop in air temperature. Going from 80F fall weather to 20F like what we have had the past few weeks in the San Antonio region would make for a 12% increase in drag which is inline with the amount of fuel mileage you dropped.

My trucks fuel economy increased a little at around 60k miles and has been steady ever since to my current 137k miles.

[FishOnOne]

Cummins12V98 wrote:
^^^^^. 36k on the engine?

36k bumper to bumper warranty and 100k on engine. For F650/F750 it's 250k on the engine.

[ShinerBock]

Texas Roadrunner wrote:
Our 6.7 liter truck mileage has dropped from the 14-16 mpg range on the highway to around 12-13 mpg when not towing. Truck has about 35,000 miles on it. We have seen mileage in town as low as 10.5 mpg. We have a K&N air filter which has been recently cleaned and we have added Power Service Diesel Kleen Injector Cleaner and Performance Improver to our last tank of fuel without any improvement. Has anyone had similar experience with the Ford 6.7 liter diesel. If so, what was your resolution? Our dealer doesn't seem to want to confront the issue. Thanks in advance for your help.

My brother has a 2012 F350 SRW and his lifetime average is around 13.5 mpg which is inline with most averages on fuelly (LINK). We also live in the San Antonio area as well and he only tows his 10k travel trailer down to Rockport a few times a year. I remember him complaining of his mileage dropping after a few years of owning it as well and I believe it is still the same way.

Although many things decrease your fuel mileage during the winter like winter blends fuel that was already stated and even the cold air itself. Air becomes more dense as it gets colder and if I recall correctly from one of the fuel economy studies at Cummins, aerodynamic drag increases by 2% for every 10F drop in air temperature. Going from 80F fall weather to 20F like what we have had the past few weeks in the San Antonio region would make for a 12% increase in drag which is inline with the amount of fuel mileage you dropped.

[Cummins12V98]

^^^^^. 36k on the engine?

[Chiefcpo]

Reinstall your filter to original, then have the shop reflash your ECM. Your 36,000 warranty is about up so he will make money very soon.
My Thought Your Tow

[hondapro]

Throw away the K&N replace it with the stock Motorcraft filter.The winter blend fuel is affecting tour fuel economy

[FishOnOne]

The 6.7 Power Stroke pulls major air volume thru the air filter. Be very careful of any aftermarket air filter.

I also agree with the ones who state winter blend fuel affecting fuel economy.

[larry_barnhart]

we had an K&N filter on our 8.1 chev and it didn't let the dogs out but let the dirt in. Very surprised what we saw in the intake tube.

chevman

[Cummins12V98]

ScottG wrote:
I agree with the others, probably winter blend fuel. I would lose that K&N as well. They have their place but never on a turbo diesel.

I have ran the AFE big cone type oiled filter on my 98 12V for 300k no issues. The difference my truck has NO SENSORS.

[ford_truck_guy]

I had the K & N on my old Ford V-10 and it had its place there

[ScottG]

I agree with the others, probably winter blend fuel. I would lose that K&N as well. They have their place but never on a turbo diesel.

[ppine]

Something ain't right. Diesels need air flow in and air flow out. Check your fuel filter, exhaust system, and sensors.

I really like the AIRE air intake and have a 4 inch exhaust. With a simple tuner your mileage can be increased. It sounds like something else is going on that should be easy to find with a computer.

[ACZL]

Winter blend fuel (x3 or 4) in your area due to recent colder than normal temps, esp in TX.

[Cummins12V98]

Personally I think the mileage you are reporting is REALITY. It's a BIG/HEAVY truck it aint going to get great mileage. Yes winter fuel does matter.