Oldsmobile/Buick Repair: 1992 Buick Lesabre, air fuel mixture, fuel milage

Question
This car has 125000 miles. It used to get 20mpg around town, 26-28 highway. The past couple of months, no matter where or how I drive, the mileage is 20-21 mpg. No trouble lights have come on. It seems that the fuel system has gone into a default mode setting using the same air fuel mixture no matter what driving conditions or speed.

Thanks.

Answer
Hi,Rick
 
You have an 7-8 mpg drop,though it may not be a cause for concern unless the vehicle does run different,does it have a loss of power?missfire?also have you tried a different grade of fuel,at 125k miles,has the engine been tuned up?usually a set of spark plugs would all that be needed or a change in fuel grade,also fuel companys have changed the fuel grade to the summer grade fuels,these fuels are less of a volitility rating,though the octane remains the same the volitility of the fuel has changed compared to the winter grade fuels,this has a small impact on fuel milage,and i am begining to have customers complain about there fuel milage,i would check to see if the engine performance is ok,if all is good,then i would monitor your MPG and see if it drops way below normal.let me know if you need more help.Thanks


ED