I just pour it in the PCV vacuum tube after driving around for a while. I let it sit for 5 minutes and then start the car. I then let it idle and rev it a few times and then go for a short drive. This stuff makes the car feel 100% smoother. With our pig rich MSP's, I don't see how it can hurt the car to do it at every oil change. They also make it in a spray form that you can spray into your throttle body. My throttle body always looks clean when I pull on the hose, so I haven't tried that.
Its the best $5 that I have spent for the car! Try some today if you never used it. 1/3 of the bottle works just fine, no need to dump 16 ozs in the car.