Should be around 22-24 mpg approximately. Not too good news as fuel prices are always continuing to increase. Why not convert to a custom water hybrid. Should reduce your consumption on fuel by at least by 35% on average, while being cleaner to the environment. Your vehicle life will also be prolonged due to less carbon build-up and engine operates at a lower normal operating temperature. These to factors increase the engine's life. You can see an interesting article on Hybrid Conversions and Technology here. Good luck with your fuel consumption.