I would put a thinner hydraulic fluid in there. Hyd fluid like ****** fluid is pretty much all detergant. I keep a half full bucket to soak rusty parts I'm using over. Also when I do headgasket jobs, mostly 4 cylinder kubota diesels, I fill each cylinder and let it soak while the head is out for service. It pulls pretty much all the carbon off in a couple days. I'm not saying kroil woundn't work, but I think it would get pretty spendy quick.