I bought a 2009 Scion Xb in April of this year 2021, it had 92,927 miles on it.....it's carfax report said it had been oil and maintained at all the right intervals..I have only driven it at a 1000 miles since buying it.  I have noticed that the gas mileage is very poor.  I just filled up the tank yesterday and it said it had a 246 mile range! It also says it is getting about 20 miles to the gallon....how could that be? Should I replace the plugs? What would be causing such crappy gas mileage? It drives perfectly, idles very smoothly, has lots of get up and go...I have had the air conditioner running, would that cause it to be that bad? Thanks for your help.