I believe that on SOME vehicles, yeah it does do some good. just not all like they claim.

look at it this way: they put the eclipse out of its misery since it's current owner obviously had no idea that "piston" is not an emotion the car goes through. And they did crush a civic and tbone a focus. 

you only paid $15? i remember seeing 'em for around $50 or $60. but i haven't seen 'em any time recently—been a few years or so. that would be a waste of money, if you paid the latter price, for such a minimal gain, imo. but i guess $15 ain't so bad. heck, i've blown more on less