Depends on how you use it!
The habit of the American automobile has been to put more engine than necessary in a car. So, if your vehicle is already over-engined, adding a turbocharger will not do anything more than to launch your vehicle off the line quicker!
But, if you put a smaller engine in your vehicle, underpower it so to say, then a turbocharger will add *TREMENDOUS* advantage to the gas mileage of the vehicle!
When Oldsmobile put the first turbocharger in a production car (the 1962 Jetfire) it was added to a 215 Cubic Inch engine that barely put out 150HP...and this to push a 3,000+pound car. The turbocharger was able to get this car to launch quickly off the line yet the smaller engine was able to sip fuel on the highway...as long as you can keep your foot out of it!
