How much do you guys get on a full tank? And how big is the tank? Thanks guys!

 

My last tank only went 209 miles on 20.5 gallons of gas. It usually is around 240 miles on the same amount of gas but I'm just having problems with my t-stat so my truck is burning extra gas because it is in a warm up mode for a long time. I will get to it this weekend. The tank in these things are like 25/27 gallons it think...