For what it's worth, I had great success with the HotShotts. When I bought my truck with 212,000 miles, it had one cylinder that, as my dad described it, "sounds like it's fighting itself" until it warmed up. Next oil change (dino), I threw in the HotShotts and ran a couple of tanks of diesel with their fuel additive. It wasn't an immediate change, since the product had to work it's way into the injector and then go about breaking down and flushing out whatever was causing the stiction. That being said, a year later when my dad rode in my truck again, he was amazed at how much better it sounded and ran. It was a gradual change, so I didn't notice it getting slightly better and slightly better. But when he said that, I remembered how bad it really had been and what an improvement it really did make. Take it for what it's worth, but it worked well for me.