Carbon on a pampered engine is not a paradox. It is almost predictable physics. Low revs, light throttle, short trips: that mix keeps combustion temperatures modest and exhaust gas velocity lazy, so soot, unburned hydrocarbons, and oil mist can plate onto valves, piston crowns, and intake ports instead of being swept away.Hard, brief accelerations on a fully warmed engine are closer to housekeepin...More