I PURCHASED MY SONIC IN APRIL OF THIS YEAR. I WAS INITIALLY WOWED BY THE AVG MPG I WAS ATTAINING BASED ON THE AVG REPORTED BY THE CAR'S COMPUTER. AFTER A FEW FILL UPS I REALIZED I WAS ADDING MORE GAS THAN THE MPG WOULD INDICATE. SINCE 6/21 I BEGAN RECORDING THE DIFFERENCE REPORTED BY THE COMPUTER AT EACH FILL UP & MY MANUAL CALCULATIONS. THE DIFFERENCE THRU 10/17 AVERAGED 5.6MPG (A LOW OF 2.3 & A HIGH OF 8.4 MPG) ALWAYS HIGHER. I TOOK IT TO THE DEALER & WAS TOLD THERE WAS NOTHING THEY COULD DO & THAT THE SVC MGR'S CADILLAC HAD THE SAME PROBLEM. IN FACT, I WAS TOLD BY HIM THAT THE COMPUTER'S FIGURE WAS THE "MPG THE CAR WAS GETTING AT THE MOMENT, NOT THE AVG SINCE LAST FILL UP. I'VE CALLED CHEVROLET, TOLD NUMEROUS PEOPLE ABOUT THE PROBLEM. I WAS PROMISED CALLBACKS & HAVE NEVER GOTTEN THEM. *TR