While 22 MPG is at the low end of the range for Volvo gas mileage, but not really awful if you have an automatic, there may be a problem with your method of measuring. Putting in the same amount of gas each time will not give you an accurate reading. What you need to do is fill the tank to the same LEVEL each time. Probably the best way to do this is to always use the same pump, at the same gas station, every time, and fill up until it shuts off automatically. Do not top off beyond that. Then drive as usual. When you fill up again, (same pump etc.) the car will be sitting at exactly the same angle, and the automatic mechanism will (hopefully) shut off at the same point, giving you the same fuel level as the previous time. Then figure your mileage. Repeat this process several times and average the results. This should give you a fairly good picture of what kind of mileage you are getting.

If its still low, there are a number of things to check:

Tires---can use somewhat more pressure than the label recommends, but do not exceed the maximum figure on the tire sidewall. I usually run 32-34 all around. This will make the ride somewhat harder, but steering feel will improve.

Air filter---if it is dirty, the engine can't breathe easily. This hurts mileage.

Tune-up---plugs, plug wires, cap and rotor. If they've been on there a while, (15K for the plugs, 50K for the other parts) replace them. You don't need fancy super duper plugs. Bosch Copper or Regular NGKs seem to work best in these engines. Don't buy cheap off-brand tuneup parts.

Thermostat---if it is broken, and the engine never fully warms up, mileage will suffer. You will also notice weak heater output.

Front end alignment---if it's off, there will be extra rolling resistance. Same if the brakes are dragging.

Splash pan---car is more aerodynamic with it in place.

Roof rack---if not permanently mounted to the roof, take it off when you aren't actually using it----big contributor to air resistance.

Wash and wax---the difference is small, but it is enough to make it cost efficient for the airlines to wash their planes regularly.



Unfortunately, there are a number of factors that you can't do anything about that can put a big dent in your mileage, such as city driving, lots of short trips, cold weather etc.