Bought a 1995 LS400 (Black on Black) with 131K. Engine was rather dusty and dirty. Every owner has their own views as to keeping an engine
clean. I'm one of those owners that like to have a clean engine so as to spot leaks and/or problems in the future. I wipe as much of the engine as I can with some clean rags and brush sludge with a soft toothbrush using Simple Green as a cleaner. Simple Green is a mild, non-toxic degreaser that does a great job. Then use WD-40 and Armor All to make it shine. I've done this procedure on about 10 ten cars and have never had a problem and get complimented by the mechanics who who see it.