oil additive...
It makes the car run smoother and quieter for about a week. I am usually late to work in the mornings so I don't warm up the Jeep too long, less than a minute most times, so I feel more secure knowing that I've added something to the engine that supposedly protects the engine better than just oil by itself.
I wouldn't think it would hurt the engine, but it does cost about $20 per shot.
I agree that if you're already using synthetic, then it probably won't help as much.


