A lot of the small engines(Kholer, Briggs, Honda) carbons up because of the low idle in pesticidal application. I've used the FP/LC and was very impressed with it's results. In fact a little as 1/2 oz(which is still too much, have brought it down to 1/4 oz)in 1 qt of oil is more than enuff in the Kholer and small engines as there is no oil filter. After the 2nd dose of LC, the oil stayed cleaner and lasted twice as long. It just didn't get as dirty. I've done the piston soak which I would recommend on these Kholer or Brigg engines and what came out was dark jet black carbon that was brokened down. Engines run like new.
FP is another story. We've got some real carboned out Honda, Kholer and Brigg engines that has stubborn carbon build up. I had one Honda engine that kept dying out cause of carbon build up. Nothing but black smoke exhuast. I poured in 1 oz FP/1 gl of fuel and like instant start no misfire and ran with no problem. In diesel application, I notice no black smoke after a couple of tanks(5 gl capacity). I've tried MMO in the same application, but the black exhaust was still there.
I really believe in extreme carboned type of small engines which usually has no oil filter...the LC/FP does some amazing positive things. I hope this helps.