in order for an automobile engine to function , three things and necessary: air , fuel and a spark to ignite the air/fuel mixture and create an explosion. the precise instant of that explosion must be such that the MAXIMUM POWER IS DELIVERED TO THE ENGINE PISTON,this is "Timing" Each engine manufacturer determines at the factory the exact timing necessary for various engines so that each ounce of power is obtained from every gallon of due to normal engine and ignition system ware , the timing can change and will reduce both power and mileage. with the Xenon timing light, the car owner can reset the power and mileage. With the Xenon timing light, the car owner can reset the timing to the new car standards and regain lost power and increase mileage.