Just got a new 2010 Golf gas, AT, and got 32/34mpg Saturday night on city/backroad driving,~45 minutes down towards the end of the first tankful. Next day, Sunday, yesterday, got 42mpg on the highway, and climbing, when I got off of the highway. Filled it up, now getting 30.7 highway mpg. Why the lower mpg? Different brand of gas from what the dealer gave me with the car, or weight of full tank, vs empty tank? Best milage on last one-third of tank.