1999 Ford Ranger 3.0 with 168,000 miles. The truck had an issue where sometimes when I started it (cold), it would run rough and throw a misfire code. It progressively got worse to the point where it was happening practically every time I started it. I knew it couldn’t be the spark plugs because they were practically brand new with only about 5,000 miles on them. So, I decided to try an injector cleaner as my first troubleshooting step. I chose B12 Chemtool because it was cheap and I understood that it was one of the more powerful cleaners. After pouring the entire 15oz can into my tank and filling up, it only took about 10 or 20 miles before I noticed that the starting problem had gone away completely. I am honestly impressed enough that I wanted to submit my testimonial to this website because I hope this product is able to help others as it has helped me. I plan to use B12 Chemtool in all my cars routinely, say, every 30K miles to make sure the fuel system in clean to prevent this problem I had with the truck.