So got my insight 2 weeks ago silver 02 m/t 186k miles new ima from dealer a year ago. I've learned lean burn and am not new to hypermiling techniques. My first tank netted me 51mpg I was extremely disappointed as I drove very conservatively. Unfortunately the car has 17"aftermarket wheels and low profile tires. I do have them pumped to sidewall Max. Could the wheels make a 20+mpg difference? I know the factory ones are 14 and very light. Also I have a check engine for the cat converter p0420 but the power doesn't seem to be affected. I'm using torque app for engine monitoring. Any opinions?