Car is 13 PP with 113k had code for bad upstream 02. So I replaced both upstream with OEM fro Rock auto, then 2 days later had the plugs replaced at the dealer. Before that I was getting about 14.5 mpg with very heavy stop and go traffic between home and work. After 12 mpg. This all was on Sunoco 93. Was really hoping my milage would have gone up after 02's and plugs, surprised to see it go down. Its been at least 4-5 tanks with this new consistent 12 mpg.