Holy crap that's already the mileage of the full-sized A/T SUV I drive, and diesel is cheaper!

Start with a good tune up. Change all the filters (air, oil, fuel). Use the correct fluids (especially engine oil) and the spark plugs specified in your owner's manual. Have the timing checked also (using a timing light). Your timing might be too advanced causing a rich mixture.

Remove all the unecessary junk from your vehicle. On one vehicle I cleaned out, I had a sackfull of junk afterwards.

Check tire pressure also.