How Can I Increase Fuel Efficiency On My 2007 Ford Taurus .....?

You have not mentioned which engine you have here. Here are the best things to do. Since this car has relatively low mileage, you probably do NOT have a whole lot of sludge present. Use SEAFOAM, anyways, and switch to Mobil One 0W-30 oil, This will reduce engine deposits, reduce friction, clean the lifters as you drive it, and get you the best power and MPG's. Remove and clean your Idle Air Control Valve (aic) using gum-out and Amsoil Foaming Cleaner, if you can find it. Clean the throttle body and plate on BOTH sides. Flush the two chemicals I mentioned above through your PCV valve and hose.This will remove any carbon on your piston rings, and valve heads and stems, You are doing the right thing by using Chevron, as it is one of the highest rated, top tier fuels around. Use ONLY genuine Ford coolant in this car. Remove the spark plugs, and use either Bosch Fusion or Denso Iridium plugs. These are a little bit more efficient thant the factory plugs, and will wring just a bit more power and fuel mileage from your car. Another pointer is to get the best, fuel efficient tires you can. Michelin Green "X" tires are one of the best. It has to do with rolling resistance, a quality not usually measured or listed on the side of the tire with other info like treadwear, traction, and temperature ratings. Use the "Tire Rack" as a guide for this. Believe it or not, keeping the car clean and waxed will also reduce drag and improve fuel economy. Keep your engine bay as clean as possible ALWAYS. Showroom clean is the best.