1). Preventing excessive piston ring wear 2). prevent valve stem seal "hardening" over time, and basically keep all the seals in good shape 3). Keep rotating parts and internals in tip top shape 4). Prevent the engine from having excessive blowby at a later time (I Hate seeing a high mileage engine with 3" of old oil stuck to the TB and crankcase vent tube) Are these valid reasons? If so, would Group III "synthetics" NOT fulfill these reasons? Meaning, are PAO synthetic engine oils the only ones capable of fulfilling these 4 objectives?