My 1990 Bonneville LE has been getting really bad gas mileage lately, about 15-17 mpg. I don't drive hard and have a mix of highway and city driving. I need to get at least 22 mpg, which is what I usually get. Last time the mileage got this bad was about a year ago and the check engine light was on so I replaced the O2 sensor.
I needed it quick to pass emissions so I just went to Autozone and bought a Bosch (I know it isn't a good one
), what is the good brand to get, and is that what I need to do?