not a big deal. Just wanted to clear up any issues that may come up.

I for one have been working all my life in the business and can list a ton of things that could cause low mpg`s but with out hands on testing to see what is going on is like trying to drive with no eyes you are just asking for trouble.
I never told any of my customers what could be going on. I always told them get it in so I can check it out. same for the OP., check it over and test it. then you know whats up. I wish the OP., the best of luck with the issue.

 

Jumping in here, I run all of my vehicles until the fuel light comes on and then I fill it up and calculate the fuel mileage, if I noticed a huge difference in mpg's like that I would slow down and diagnose the problem. But most important is an accurate average of mpg's over an extended period of time. I am just now starting to use my gps for mileage, hopefully better accuracy will be the result, since my tires are not stock size.

p.s., I have only checked 1 tank on my 04 F-350 SRW, that I bought last week (15.4 mpg's)

 

This is my plan.

I'm going to replace my up pipe, and do exhaust manifold gaskets this winter.

It's really the only time I can really get a garage and leve it for weeks at a time if I have too.

Plus it gives me time to save up extra cash.

Then I will see how it goes, I also think I'm going to do my stc fitting, dummy plugs and stand pipes. Just to ensure there is no leaks.

I will also probably re o ring my injectors at the same time.

 

get all the work you want don`t while you can and good luck.