So last week i cleaned my throttle body and put in some stp fuel injector cleaner in a full tank of gas, and pumped my tires up bc they were low. normally i get 14mpg consistently, which is bad enough. i expected to get 15+ after doing this little tune up, instead i just got 11.5mpg on this tank under the exact same driving conditions what in the heck is going on here?

its a 2001 5.4ltr with 130k miles

 

Colder weather, winter gas? My mpg's wayyy down in past couple of weeks but this is normal for my location/time of year.

Keep track of the MPG's for a few tanks and report back, could just be an anomaly.

or the STP snake oil. check out S1 or regane (seriously)

Nice lookin' rig by the way and she's dialed in with yer modz

 

ill see what i can do. thanks for the compliments tho, i need to get my pics up of the black tail lights it really looks different

 

Techron is the best gas additive.