I use the stuff in the top you posted. Not for any real great reason other then I have some I use in my gas engines. I do not tune an engine to a smoke trail but I fly with a few fellows that will fatten up an engine until it looks like it's on fire and think they have it in correct tune. Not all fuels and not all blends will leave the good old smoke trail. Fuels have improved a lot over the years and there blends may not have a lot of Castor in it. When I started adding the two ounces of Klotz to my fuel I did get that good old smoke trail and it made the old farts very happy to see it. Keeping the peanut gallery quiet is just another small bonus. If I have 18% oil in my blended fuel I don't ever add anything to it at all.