1999 Bonneville Sle gettin horrible gas milage
I am in a pickle and can not figure out why I am losing so much gas milage. I am currently at 99k miles. I recently change plugs, wires,air filter,o2 in the manifold, new tires with right pressure and alignment. Getting 325 to a tank around 18 miles per gallon. I drive 1 mile to the freeway then 27 freeway miles and 1 more mile to work each day. I am stressing here that 27 of my miles are freeway and I do not sit in any traffic. Tomorrow I am changing the o2 sensor after the convertor but believe that will not fix the problem. Check engine light is not on, and not burnt out either. I hat paying 100 bucks to have it checked at the dealer so help me with some suggestions as to what I may be missing her.