I bought a 2006 automatic, featureless, Ford Focus in October 2012. I took it to my mechanic to have a buyer’s inspection and it had zero issues (after a previous car taken in had pages of issues). I am a hyper-miler, I got 34MPG City and 38 highway on my 2000 Saturn SL, which was of similar size and features as the Focus. I’m only getting about 18MPG. I’ve had the oil changed, I keep the tires inflated, I use my bike/legs to make short trips, I’m not hauling anything. What might be causing this?
Is the Check Engine Light on or are there any codes present?
How are you determining fuel mileage?
Have your mechanic check two things
A thermostat that’s stuck open. If the thermostat is stuck open the engine doesn’t get to the proper operating temperature and engine uses more fuel.
A defective coolant temperature sensor for the computer. If this sensor has failed where it’s telling the computer that engine never gets up to operating temperature when it actually does, the computer will think the engine is still cold and the engine uses more fuel.
Tester
In addition to the great advice that you’ve already received your Focus only has a combined fuel mileage of 26MPG. It’s 23 city and 31 highway. If you have one or more dragging brakes or a mechanical issue then 18MPG would be about right. Where is the majority of your driving done? In the city or on the highway?