99 chevy metro

i have a 99 chevy metro 1.3, 116k

i bought the car in may and it was geting 38 mpg and in nov from one day to the other i started to get 28 mpg still runs great but the idle seems to low

i change the plugs, the wires, coolant sensor, 02 sensors and still 28 mpg

ANY BODY OUT THERE NOWS WHAT IS GOING ON? PLEASE, THANKS

How do you calculate mpg? Hopefully by filling; recording miles driven & dividing by gallons at the next fill up. Its the only reliable way.

You will get lower mileage in the winter (maybe 10% avg?)

Check your tire pressure - like a lot. When they’re cool in the morning before driving.

Check your air filter & replace if necessary.

Change the fuel filter.

Run a can of sea foam thru the gas tank.

Have the brakes checked for sticking/dragging.

If there is any hint of an alignment problem have it checked.

Run the defrost or A/C as little as possible.

Did you add anything such as a roof rack?

Did your driving habits change? (city vs. highway).

Try to always drive downhill with the wind at your back (ok - that one is obviously a joke).