You say "about". How are you getting at this number?====First thing is to accurately measure your MPG. To do this you start out by filling the tank FULL (extremely full). Don't stop at exactly $10, $20, etc. Full that tank until it just won't take any more fuel.Now set your tripometer to zero and go for a drive. The longer the drive the more accurate. You should do this after rush out to get better accuracy. Now note the mileage (10, 20, 30 or whatever mileage). As close to the HWY, go and fill the tank again. Again fill it to the MAX. NOW note the GALLONS. Divide MILEs by GALLONs. MPG = Mile / Gallon.===The reason you fill it the first time is to start at an "repeatable point". ===You can always try and improve your MPG by (a) getting a tune-up - new plugs, wires, distributor caps, rotors, igniting timing (b) make sure you have enough air in tires (c) most importantly drive mildly. Your driving habit probably effects your MPG more than anything else.