I have used Berryman B-12 to clean motorcycle carbs before and this stuff literally dissolves crud and black scum faster than anything I ve seen. I ve used it to clear up small engines and I might have even got carried away with a old Lawn boy mower. I didn't care if it blew up, I was just disgusted with its poor performance. I started it up and it blew white smoke for at least 10 minutes and spit black crud out the muffler. It now runs like a top and its been months. Starts first pull every time, so I know this stuff works. My 5.4 had a rough idle. I loaned it to my son for a month and he probably put the cheapest no name gas in it, he could find. It sat a lot too. I had a nice 300+ mile road trip over the weekend, so I thought this would be a good time to clean it out. I will try Berryman B-12. Frankly, I am a little scared of the stuff. I have seen it dissolve varnish and melt plastic mixing cups. Its powerful stuff. I added a pint to a full tank, about 20 gal. The truck drove alright up, by Georgia, the idle improved dramatically. It smoothed right out. The truck felt a little sluggish, but the idle was now smooth. I topped it off with 93 and drove it home. Runs Great, I think I will now dose my other vehicles. I will definitely not get carried away with the stuff. I will say its one product I approve of. It works. I also feel my gas mileage improved although I didn't check it. I definitely used less fuel coming back. I use Marvel Mystery oil in all my cars and trucks and believe its good maintenance program, but not a serious cleaner. This B-12 is.