I'm usually the first to knock down the claims of "snake oil" additives in anything but the first gen cummins I bought recently has always had a weird rattle to it. A rattle above an beyond the normal 12v clatter. There was one cylinder in particular that was extremely loud. Any type of load or RPM would make the rattle/knock more apparent and was bad enough that I thought wrist pins or rod bearings. I would hear the knock echo off of jersey barriers on the highway even.
I was in the farm store looking around and I was in the oil isle, I was reading some of the bottles just for the entertainment and I found a bottle of this.
http://www.hotshotsecret.com/shop/diesel-extreme/
I thought, why not, its worth a shot. I was already in the market for a set of injectors to fix the problem so whats 25 bucks.
Today I filled up and actually put in 32 oz (Brain fart, somehow thought 16oz was a quart). I am absolutely thrilled how it worked. Before I even got on the highway from the gas station I was noticing a difference. By the time I got home (20 miles) it was a whole new truck, I just can't believe it. I had a slight lope at idle hot and that's gone. The knocks and clatter is gone. The turbo spools sooner, and a lot less throttle is needed now. Definitely a believer already...