A friend has a 04 Accord 4 Cyl with 76,000 kM (47,000 miles) and his MPG has decayed from about 38 to 22 MPG (Imperial) over the last 2-3 years. Any ideas? Could it be a Catalytic Converter issue? Thanks for the anticipated help.

 

there are a zillion possible reasons, some of them that I have heard of are:
-plug wires/plugs
-engine sludge(try gummout all in one cleaner)
-TPS sensor
-distributor cap
-bad ground wires
-fuel filter
-fuel injectors
-dying battery
-rims that are excessively big
-too much extra crap in your trunk(extra weight is a big one thats often overlooked.)
-lots of new electronics with stock alternator

Im sure someone can list some more. A tune up will cover most of the big ones if you dont want to do the work yourself. goodluck.

 

yeah when was the last tune up? A tune up will usually fix this problem. If nothing has been done to the car maintance wise I'm almost sure this will be the problem.