I just bought a 2009 2.4i FWD (5Sp. Geartronic auto) with only 36,500 miles from a dealer and the car has got the worst gas mileage ever. I spend about $160/mo on fuel driving only 5 days/wk to and from work. Whenever the tank is filled, I reset the trip to 0.00 and by the time it gets to 170-180, the meter has already gone down to the 1/4 mark! This puts me at an average of about 15-17mpg 50/50 city/fwy!!! Also, my receipt shows an average of 11-12 gallons. I thought this was a 14.9 gallon tank -- give or take for 'reserves' but where is the rest?

I do understand that this is an inline 5 cylinder but my 2008 Audi A4 2.0 Turbo 4-cylinder (which weighs a ton) gets better fuel mileage!
The first thing I did was replaced a genuine Volvo Air Filter for the S40 even though it looked pretty clean. I also checked the tire pressure and made sure they are at around 39-40psi but nowhere near the max psi for safety reasons. The dealer did all the necessary maintenance before they put this car car up for sale. The previous owner also had the vehicle serviced in Sept. before it was traded-in (I bought it in mid Oct).

What can be the issue here? Nice car but hating the gas mileage so far.

 

Check the exhaust. Anything clogging the tailpipe? Does it feel low on power? It must be running rich if it sucks that much gas. Pull the plugs and check their condition.