MPG dropping

landp

Well-known member
I have and 06 diesel f-350. When I purchased it I got right around 16mpg(without towing), now I get 11 to 12 MPG(again without towing). Is there something I can do to get back to 15 mpg or is the new fuel to blame? I have my truck serviced by ford and always on schedule, so I cant imagine they wouldnt have taken the opportunity to change filters or such.
 

nhunter

Well-known member
Have they changed the air filter. The dealerships like to wait for the indicator but I had 70000m on mine and the indicator still siad it was good. I changed it anyway. I heard the new fuel doesn't help either.
 

TXBobcat

Fulltime
landp
I have a 2006 F250 that I took delivery in February 2006. I originally got 10.5mpg pulling my 3400, 14-16mpg in town without the trailer and around 16-19 mpg on the highway. I have about 71K miles on it now.

In October of 2008 I pulled into a place to have the axles on my trailer replaced. When I pulled in my truck was running great. When I pulled out it was laboring. I checked the wheels on the trailer to make sure they were turning properly, and they were. My gas mileage went down about 2mpg. When I was not pulling the trailer it ran pretty good and the gas mileage was about the same. I just knew that they had done something to my trailer to cause it to pull hard.

While in Mission TX this March the check engine light come on. It went off later in the afternoon. Well when I went to start my truck the next morning it would not start. Had Coach-Net so I called them and had them take the truck to Spikes Ford Dealership in Mission. By the way this is a great dealership.

They tested the truck out and found that the injector module had gone out. However they told me that if I had taken the truck to the dealership when the check engine light was on they would have only replaced the #2 injector. The tech told me that the injector module was a very common problem. All the work was done under the 100k warranty for the diesel engine. They also covered the rent car cost except the tax. Well now my truck is pulling like a champ. Infact I am getting close to 11mpg pulling the trailer.

You might take the truck in to and have them check the injector module. However they told me they could not have changed out the module if it had not indicated a failure in the computer tests. That Sucks..

Also I have had no problem with the ULS Diesel. I talked to a mechanic that works on big Semi truck engines and he did say to use a additive in the fuel. He suggested the one you can get at Wal-Mart in the gray plastic bottle. I have a 38gal OEM tank and a 45gal add on. I use one of the 16oz bottles every so often. Check out the instructions on the bottle.

Hope this is helpful to you.. Good luck.
 

Del600

Iowa Chapter Founding Father
Well first off I was going to say you maybe getting winter blend diesel, but you're in texas, so I am not sure you guys run it down there.
My 06 Duramax gets 20-21 on the highway with summer fuel, during the winter blend months mine drops to 17-18 un-loaded.
 

JohnDar

Prolifically Gabby Member
My new '09 GMC has 700 miles on it so far and I'm getting about 12.5 mpg. Haven't towed anything yet. Been adding about 4oz of Diesel Kleen (the WalMart stuff) every half tank fill-up.
 

Clark

Member
No answers, but just as a comparison, I have a 2007 Chevy 2500 deisel and BH3055RL. Milage is about 28000. I get around 12.5 mpg pulling, 22 mpg straight highway, and 18 mpg mixed town/slow driving. Big factors to drop mileage are: headwind when pulling, uphill towing, mountains. I know that these are all known mileage killers, just wanted to throw them in. Filters and injectors are two variables that may be at fault.
Clark
 

jmgratz

Original Owners Club Member
I was getting 11-12 towing before with the regular diesel. Now it is 9-10 with the ULS diesel. The new diesel sucks. Truck uses more fuel so doesn't that equal more emissions? I thought the ULS was supposed to lower emissions. Go figure, just like the government stuff. Screwed up.
 

Peteandsharon

Well-known member
I've also noticed a decrease. Haven't done an actual mpg calculation in a while but I have noticed that a tank of diesel doesn't go as far as it used to go. We do have winter blend up in northern Illinois so that is part of it but I'm sure not all of it. This week I am trading my trusty 7.3L for a new 6.4L Powerstroke. I'm already preparing myself for the shock. I'm very excited about what the new truck will give me but MPG is not one of them.
 

jmgratz

Original Owners Club Member
I've also noticed a decrease. Haven't done an actual mpg calculation in a while but I have noticed that a tank of diesel doesn't go as far as it used to go. We do have winter blend up in northern Illinois so that is part of it but I'm sure not all of it. This week I am trading my trusty 7.3L for a new 6.4L Powerstroke. I'm already preparing myself for the shock. I'm very excited about what the new truck will give me but MPG is not one of them.

Keep us posted on the difference you find. I have heard from some the 6.4 is more powerful. Go figure.:cool:
 

trvlrerik

Well-known member
I have attempted to do different things to get better mileage out of my 08 f350 6.4, and the only thing that seems to make a difference is to keep the engine between 1700 and 2500 rpm. That gets me 10-12mpg in nearly all conditions (wind, hills ect.) On a flat run with a 15600lb trailer that is about 65-70mph. Any rpm above 2500 rpm and mileage drops to around 7mpg.
 

Uncle Rog

Well-known member
My Story.....

I have several friends who have used Mobil 1 for years in all their vehicles, they have also ridiculed me mercilessly for using "oil".
Two weeks ago I switched to the synthetic, 5-40, Turbo Diesel blend.
My shop man wanted to mess with the AFE air unit so bad, but no reason to.
He DID spray off the MAF sensor which, after 75k miles, was a might dusty.
Here is the dealio, prior to changing the oil and spraying off the sensor the OBC read 15.2 mpg. That is all driving, freeway, city driving, off road, done. After the change, and spray it reads from 16.6-17.2, varying from different types of driving.
I have hesitated to post this prior to now because I wanted to give it a couple of weeks to really see if the results would stick.
So now, what gave me 10% better mileage, the oil or the clean sensor?
Two things to note, the truck does seem to run "smoother" to me and the OBC mileage is usually optimistic by 1mpg over hand calculating......
Who knows.............
 

Bob&Patty

Founders of SoCal Chapter
Rog, Ken (katkens) and I are working on something that will help performance and mileage. I going to do it on mine 1st. If it works I will let you know. It only works on the VIN# 2 motor. My part is ordered but its on intergalactic back order from the General. Bob:confused:
 

Peteandsharon

Well-known member
Jim,

I will let you know what difference there is. Certainly, on paper, it is a stronger engine. My 7.3 was 500 ft lbs. of torque out of the box while this one is 650 with more horsepower too. But the new emission standards are a bear. We'll see.
 

superduty08

Tennessee Chapter Leaders
I have had the 6.0 and now have the 6.4. Both out preformed my son's 7.3. You will notice a great deal more power with the 6.4. I added the 4" exhaust and a free flow air filter. This gained about 1-1.5 mpg towing.
 

Peteandsharon

Well-known member
Bobby, I've seen performance exhausts already for the 6.4. I'm just a little curious how much good they can be when you have the diesel particulate filter inline. That has to be very restrictive in itself and the exhaust system is only as good as the weakest link. I had a performance exhaust on my 7.3L but I always understood that it was not as good as it could get because I replaced from the catalytic convertor back. Just a thought. I do intend to put a K&N filter up front on my new rig at the very least, though.
 

boatto5er

Founding VA Chap Ldr (Ret)
I tried putting an AFE performance filter on mine and my mileage did go up about .5 MPG. However, the check engine light also kept coming on. Went through that cycle three times before the dealer and I both got tired of resetting it. Seems like the AFE and the mass air sensor just weren't compatible. Put the OEM filter back on and everything is back to normal.
 

superduty08

Tennessee Chapter Leaders
I have the AFE dry flow filter in the stock housing and have never had a problem with the check engine light. I have heard of others with the same problem but they had changed to a cold air induction system. On the '08 the air is chaneled from outside via the passenger side fender so I did not see an advantage worth the cost. Pete, you are correct about the DPF being the weak point. I do not even have a muffler in the 4" and the exhaust is no louder due to the DPF. I had a Hypertech programer for a trial before the intake and filter change. Had a lot more power but no better mileage. I would like to try it again with the changes.
 

boatto5er

Founding VA Chap Ldr (Ret)
I replaced the stock housing with the AFE housing kit. I actually think that was the big problem. The MAFS simply didn't mesh well with the AFE housing kit. I'm back to normal and running fine so I'll probably wait til the warranty is up and then try out a chipset upgrade and a couple of other features.
 

TXBobcat

Fulltime
I have and 06 diesel f-350. When I purchased it I got right around 16mpg(without towing), now I get 11 to 12 MPG (again without towing). Is there something I can do to get back to 15 mpg or is the new fuel to blame? I have my truck serviced by ford and always on schedule, so I cant imagine they wouldnt have taken the opportunity to change filters or such.

Just an observation.. the OP was asking about the mileage on his 350 going down and I think what would cause he mileage to go down. So far the OP has not returned... But has anyone answered his post.

Looks like to me it was Hijacked..:eek:. Any thoughts ??
 
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