Try to flush cooling system, if never did. The better you do it, the cooler engine will be. Replace cooling liquid. Also, if it is hot weather, install crankcase oil radiator, always keep oil level at max. Crankcase oild also cools down engine. Keep cooling liquid level at max. Also, you may need to clean radiator to increase efficiency. Clean mass airflow throttle, by the way check motor air filter. Check air pressure in tires, too low means more rolling resistance, especially at high speed. Hope this will help. How is your average MPG?
