looking than Kroil! ;) I have always used MMO with my Top Eng. Cleaner, but Kroil seems to work ok - Mike Bigelow recently advised me that he was using the Top Engine Cleaner straight out of the can - though it' s "not supposed to", leaving the stuff in the barrel appeared to slowly desolve copper! So, I cleaned a barrel, dried it out and then wet it down with TEC ; a couple of days later, a dry patch was pushed through the barrel; it came out green . . . HMMmmmm. R.G.