well I would bet that your injectors are kinda clogged.. making the fuel not atomize properly. what I did a few months ago was to get some seafoam and with about 3/4 full gas tank, I put 2 small bottles (treat 20 gallons each), into the gas tank and ran it til it was almost empty. It smoked and idled fairly rough, but it made me go from 12.5ish to 14 mpgs in about a week
. I have heard that techron will do the same thing. I was thinking of changing my plugs is why I did it, but now I am gonna wait til summer to change them. No guarantees, your results may vary
. but I think it is worth a shot.