1999 Honda Civic Poor Gas Mileage

Suggested Repair

Before replacing oxygen sensors, check basic items that can hurt fuel economy: ignition timing, tire pressure, dragging brakes, and the air cleaner.

Conversation Summary

The owner of a well-maintained 1999 Honda Civic with about 106,000 miles reports a recent drop of 6 to 10 mpg. New spark plugs improved power but not mileage, and the car otherwise runs well. The expert advises against replacing the oxygen sensors yet and recommends checking basics such as timing, tire pressure, dragging brakes, and the air cleaner.