Nuke

At this point, I'd run at least 2 tanks with SeaFoam mix. Although I typically add a good fuel system cleaner about every 10k miles, I save the SeaFoam for when something "just ain't right". Then go from there.

Menace

Thanks Nuke, I'll try this Seafoam stuff I guess. I'm guessing any auto store?

Menace

I mentioned the fact that I just had Ford do a fuel service a few months back ... that includes what i'm guessing is a gas fuel additive, something to do with the intake/injectors as well. Though as someone else mentioned; i'd rather not go to the dealer. The local dealer is like rated the best in two states as it borders two of them, and sadly I have experienced nothing but bad stuff with them. (To include my car stalling frequently because they didn't tighten my CAI down after said fuel service was done).

Menace

Currently the 50 miles till empty came on. I looked and I have driven 135 miles and used 11 gallons of gas. That's a little under 13 mpg. Less than 200 miles per tank if the 50 stays true to the number. Horrible.

Nuke

SeaFoam is available at WalMart and any auto parts store. But if the dealer did a PROPER fuel system service, then SeaFOam most likely won't help. I'd still do it anyway. SeaFoam can't hurt. I usually just do 2 tanks of the proper mix, being sure to run each tank down to at least 1/4 tank. I'm too faint-of-heart to do the injection method since I have a way of screwing SOMETHING up too often. I have other things that I'd rather FUBAR than the Stang...

Menace

Seafoam is in. It said 1oz for every gallon. We have a 16 gallon tank so I dumped the whole bottle in. Filled up. We'll see how it goes. I have doubts that the dealer did a correct anything.

Also, and this may be far fetched... Could lowering the car affect the transmission? The pinion angle and all, I don't know what mine is I never adjusted for it. I just have been getting an occasional loud whine from somewhere, and I get a clunk whenever I go over bumps, and can be felt through the shifter. Thinking maybe if somehow it is affecting the transmission that could also be a problem with my mpg's? I dunno, at this point I'll consider anything because I just can't pin point it.

OhEightGT

Lowering your car shouldn't have any bearing on your mileage. You're getting about the same mileage as my car does now (around town) with it's modifications! Something is seriously off, and if you can't get it pinpointed with the guys here, I'd do as suggested previously and find a good local shop. Dealers can be great, but they can also be TERRIBLE. It's hard to beat a good shop with an excellent word of mouth rep, as they are often very personal and actually appreciate and need the work, and don't just throw their hands in the air and call Ford for an excuse to stop. You might even see if you can find a Mustang specific performance shop in your area. Even with a stock or mostly stock setup, they can hook it up and log everything, a lot of those dyno tune/performance guys really know their sh*t because after mods, there can be 100 kinds of untold and unexpected problems and they are usually (if good and Mustang specific) pretty good at pinpointing things. Just a thought!

SeVeReDiStOrTiOn

Jack the car up and check for any excess drag...could have a stuck caliper or the e-brake might not be disengaging all the way.