The wear just doesn't come from the oil . The wear also comes from the richer air ,fuel mixture and the pistons are oval measure them, and the engines clearances are machined so they will be proper when the engine is at operating temps Metals expand when heated. There is more blow by in a cold engine and combined with the richer air fuel mixture the acidic blow by washes the cylinder s of oil . There is also more wear until operating oil pressures are achieved. If you look at the million mile vehicle reports they are engines that spend their lives at operating temps.Castrol claims that their research shows that it takes about 20 minutes for the sump oil to come up to full operating temperature. It is during this time frame that most of the wear occurs. They have papers written on this topic and of course there are numerous advertisements for their Magnatec product that is specifically designed to protect engines during this warming up period.