Just wondering what could be issue. I know alot of things can cause bad mpg but the thing is the message center says 18.1 cty at best 18.3 hwy now i think even if something is affecting mpg there should be more of a gap for hwy than that. the check engine lite has been on so i did a scan only to get a code that say catalyst below threshold on bank one. I think this refers to the cat maybe stopped up dunno any help would be nice thanks in advance

Check to make sure your plugs are in good shape. If you have never changed the front O2 sensor, you may want to consider changing that. If the sensor is going bad you will run rich and wear out the cat.

Thanks yea this makes since all time rich.I havent had any codes for the o2 but that dont mean anything it might be getting lazy lol. I do believe the cat is bad according to the code i got it refers to cat failure. dont know if it means stopped up or just not helping on pollution. which i think your right could all go back to o2 sensor or fuel not being burned due to bad plug. i am planing on down pipe,ubend delete res delete and install hi flow cat

oh yea ordered a fender cai for bon. i know little add but its my start

yea just so you know that is way low and should be more of a gap. but how fast do you drive highway if your doing mere than 85 i wouldnt be surprised by your mpg. a good cai got me up about 2-3 mpg average to be honest i dont know if your air box is the same as the lesabre and i just got the down pipe wow what a difference id do those two first obviously along with a tune up and o2 sensor youll get a lot better after that if you can keep your foot out of it lol