There is probably no best but, depends on your engine, type of deposits and how messed up your fuel system is. My own experience from one case is a friends worn Volvo repeatedly failing the Illinois State smog inspection. We added a bottle of Techron SYSTEM cleaner in 1/2 tank of fuel and took it out on the highway for a 30 mile 80 mph run. Passed the smog test easily. I personally use Techron System cleaner just before I change the oil (6000 Mile OCI) and never have noticed any difference but, then I maintain my vehicles and don't use off brand fuel. BMW, together with Chevron oil Co. developed the additive to keep the BMW intake valves and combustion chambers clean. BMW had a problem with their camshaft overlap that encouraged carbon buildup on the intake valves and pistons). Chevron continues to use that additive in their fuel. I really don't know if the new-comer Regane is better or equal or less effective but, I do know that Techron has a long history of excellence and I now continue to use it out of habit. Just my thoughts and experience. Maybe I will try Regane next time but, I don't know why at this point. Ed