Volvo: S70 POOR GAS MILEAGE, poor gas mileage, fuel consumption

Question
RAY,
JUST RECENTLY MY 1998 S70 NON TURBO HAS BEEN GETTING VERY POOR GAS MILEAGE. IT HAS DROPPED FROM 24-26 HIGHWAY TO ABOUT 16-18. I DO MOSTLY HIGHWAY DRIVING AND HAVE NO CODES OR CHECK ENGINE LIGHT. JUST CHECKED IT WITH THE OBT2 AT AUTOZONE.I HAVE HAD A FEW NOISES FROM THE AIR PUMP BUT THERE GONE IN LESS THAN A MINUTE.JET ENGINE SOUND. ANY IDEAS ON THE FUEL CONSUMPTION?

Answer
Dave,
If there are no codes in the system, that would indicate no engine management problems and all is fine. So perhaps the temps are real cold, causing higher comsumption longer warm up times, or the engine is not reaching operating tempature, due to a faulty t/stat or the fuel you have is a poor grade.