Terrible fuel economy

Hi guys, I am testing my luck with this form because i have been having some tricky problems with my 2001 7.3 diesel. I bought the truck in August. Ever since then I have been getting about 13 mpg. It was a little better than 13 when i first got it and now it is closer to 12. I never new 13 was low since I am new to diesels. Everyone I have spoken to agrees that this truck should be getting at least 17. A few months ago, I took it into my mechanic to find the problem. He found a massive fuel leak behind the turbo and found that the sensor for the ebpv was shot and the tube was clogged. He fixed the leak and replaced the ebpv sensor and tube. I thought that would solve all my problems, but after I went to fill up I found that I was getting 12.3 mpg. How my mileage could go down after fixing a fuel leak baffles me. I also noticed that the engine was hissing while I was driving – I assumed it was the ebpv again, so I brought the truck back in and had the ebpv deleted. I have seen virtually no improvement to my mpg. No one I have spoken to can even formulate a guess as to what the problem might be. This truck is all stock with the exception of a dp tuner with 80hp tunes. It is a regular cab with 8 foot bed and usually weights around 7500lbs. I would really appreciate any ideas for what the issue could be. I do not believe upgrades are the answer to this; I am confident that something is not functioning properly and needs to be fixed.

Your diesel and your truck have hit the wall. Without some big change like a complete overhaul or a replacement of the fuel injectors or an unclogged exhaust system or some successful diagnosis that fixes the problem, the fuel economy will stay down.

Check tire pressure because you may be way too low. You may need at least 60 PSI for that weight, maybe more.

You may be right. I don’t think I want to spend a grand or more on new injectors… maybe I could just put a lot of injector cleaner in the next fill up? How could I tell If I have a clogged exhaust? I read on another forum that someone with the same problem replaced his IAT sensor and put a lot of cetane booster in his fuel which fixed it. Is that worth a shot? I don’t know what problems I could expect with a broken IAT sensor, but it runs fine and starts ok… sometimes it grinds instead of turning over.

The only thing I said about the truck that I have any experience with is tire pressure. A diesel mechanic can check things that I can’t even name. I bet I know why you don’t want a new truck at $60,000.

The reason I dared to write a reply is because I owned a Cheyenne Super 10 Suburban, 1974 year that got 7.6 MPG with a 454 engine. I was upset at the time because a fill-up of the 30 gallon tank cost me $20.

You didn’t mention the type of driving the truck is used for, 13 in the city and 17 on the highway is about right. My father was satisfied with 10 MPG on the highway pulling a fifth wheel trailer with his new diesel truck, the V-10 gasoline truck he traded got 7 MPG.

Don’t believe tales of 20 MPG with a loaded work truck.

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It’s about 50/50. That said, I am always at 12-13 it makes virtually no difference if it’s all City or all highway. I try to always keep it under 2000rpm

Go back to all stock, and report the results.

It was the same story before I had the tuner in it

We had a discussion a while back with a tuner add-on to a Ford diesel. Engine blown.

I remember that one. It was a brand new truck that the people took on a moving trip. While climbing the mountains to Flagstaff, AZ the engine blew due to the kit and was not warrantable. Eleven grand later…

Wonder what the rear axle ratio is in this one? And tire pressure?

It’s got 3.73 gears. Last I checked, the tires are 65psi all around.

You shouldn’t try to keep the engine speed down. Normal engine speeds will keep the combustion chambers cleaner with a diesel.

Yeah I remember that $11,000 repair. Didn’t remember what caused it though.