i would not use it in oil. glad you god your misfire whipped. i have one that comes and goes. usually when we have drastic temp. changes. of course you know how moody they can be. An engine lubrication system cleaning...i would use some trans fluid, or even dr. marvel's mystery oil, to top off (or slightly overfill) the sump and drive it for a few days then change oil like you always do. lots of us have our opinions on the subject.