I am sure it will be fine, but I would not give a new car/engine a steady diet of high mileage oil (with its extra additives to swell seals). I would not give a used car HM oil unless it actually had a problem with a seal (not a gasket) and the problem was not seal damage. Synthetic oils especially have great conditioners for seals. If the area around the seal is kept clean by quality oil, the seal will be conditioned and should not leak.