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Over the last 2 months I've noticed that my fuel economy has been getting worse and worse.

I started off with about 17.5mpg hand calculated with the tripometer and the amount put in the tank. Filled it to the brim every time so I know it was almost exactly on as to the fill level every time.

Then it started going to 16mpg, then 15, etc... Now I'm down to almost 11mpg.


Fuel filters were replaced at 70k and I'm at 77500 right now. so those shouldn't be clogged up. Running Mobil1 5-40TDT. Dieselsite coolant filter.

I usually only fill up at two stations. One near work that has an ok price on fuel and one a little further out that stocks Biodiesel. Most I've ever ran was B20 and it's usually mixed in with 1/4 to a half tank of No.2. Also I run Stanadyne at the suggested mix on the bottle.

Any theories as to why this is happening?

-Mike
 

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I'm guessing they have switched to the winter blend, but I don't know if they do that in your part of the country. They have to where I live and my mileage has dropped since October.

Part of owning a diesel and winter, I guess.
 

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I would have to agree, IT IS THE WINTERBLEND OF FUEL. You may want to have your fuel filters changed they may have gotten clogged or some gelling occured.
 

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winter blend doesn't drop it that much thou, your injectors could be on the fritzz. are you idling alot? he's also in tn im sure its a mild form of winter blend to.
 

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when mine dropped from 17. all the way down to 12mpg i took it in & had #4 injector go out.
mine alwasy drops a little in the winter but not that much, i bet u got a bad injector.
just my 2 cents.
 

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Try a cetane booster like Stanadyne...or FPPF Lubricity + Power...two good brands to help. Any other symptoms...any smoke...if so, what color? How's your fuel pressure? Anything lacking on your driveline maintenance....trans filters flush...good fluids...axle lubes...brakes dragging...etc...
 

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Idling can consume quite a bit of fuel during the course of a "tank load". Usage is 0.8 to 2 gph depending on the rpm of idle.

However, I will say that wintertime WILL decrease the fuel economy (part of it is the fuel, but part is how the engine warms up and is tuned IMO).
 

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Over the last 2 months I've noticed that my fuel economy has been getting worse and worse.

I started off with about 17.5mpg hand calculated with the tripometer and the amount put in the tank. Filled it to the brim every time so I know it was almost exactly on as to the fill level every time.

Then it started going to 16mpg, then 15, etc... Now I'm down to almost 11mpg.


Fuel filters were replaced at 70k and I'm at 77500 right now. so those shouldn't be clogged up. Running Mobil1 5-40TDT. Dieselsite coolant filter.

I usually only fill up at two stations. One near work that has an ok price on fuel and one a little further out that stocks Biodiesel. Most I've ever ran was B20 and it's usually mixed in with 1/4 to a half tank of No.2. Also I run Stanadyne at the suggested mix on the bottle.

Any theories as to why this is happening?

-Mike
My mpg drops in the winter also, not as much as yours though. Mine drops between 1.5 and 2 mpg.
 
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