Those "complex parts" (engine and gearboxes) usually only require yearly oil changes and replacement of minor parts as you mentioned (spark plugs, plug wires, b

Those "complex parts" (engine and gearboxes) usually only require yearly oil changes and replacement of minor parts as you mentioned (spark plugs, plug wires, belts, tensioners--maybe injectors every 100kmi) for the first quarter million miles. At 10kmi/yr that's 25yr. The complexity as defined by parts count doesn't have much practical impact on TCO.