I was wondering about different fuels.....MAF I can check. The 02 sensor "looks" new.
oh, and dont put full trust into the dic ave mileage. its not 100%.
the only way to really know you miles per gallon is to fill the tank, note your miles, run it down to low, then re fill the tank, now take the miles driven and gallons you just put in to figure out your mpg. simple division.
I've also been wondering about the T Stat. The car runs at 180 deg. I think I read that they do better at 220?
put a 195 in there, the car may not be warming up enough and its staying in closed loop, and killing mpg.
your engine wants to be at 210 deg's.