[a92h0ndacivic]

I am currently getting anywhere from 26-33 mpg. I have tried all different fuels/grades from different stations. Before I purchased the car, a new distributor was installed. I have installed spark plugs and a new fuel filter and am lucky to get 280-320 miles to the tank. I was thinking about swapping the engine out for a VX engine with vtec-e for the gas mileage but am not sure at this point.Does anyone have suggestions for me?

Oil is Mobil one fully syn. 5w30 changed every 4-5k, stock ECU (p28), 2.25 inch exhaust and stock air box