Many people are under the assumption that if they add a supercharger or turbocharger they will reduce the gas milage on their vehicle. This was true with older carbureted engines. With the older carbureted engines, the engine generally ran best at full throttle. Not so with the newer fuel injected engines as they mix and burn the air/fuel mixture very efficiently. During normal driving you should see very little change in gas milage. Only when extra power is used will you see more degradation in gas milage. However you will have to use premium fuel as misfiring or detination could be fatal to your engine with the high compression that is achieved. Depending on the unit installed and the other add on high performance components installed on your engine horsepowers can increase dramatically from 30% to 80%. Since more power is achieved from the engine you will not need to step down as hard on the accelerator to gain power counters the amount of fuel needed to get the power gain. Hope this information is useful and if anyone would like more information then email me at r_arntz@bellsouth.net.