I've been running Castrol GTX High Mileag in my car which has 120k and this car does not leak oil, but has some minor oil seapage. I've been wanting to stop using the High Mileage oil and use energy conserving Havoline because I feel this engine (with it's 10yrs of age and high mileage) is not a tired or worn out engine. I just hope that my idea of getting off the High Mileage band wagon won't hurt anything with regard to this motor and its engine seals. My OCI is every 3 monthss because I enjoy doing this, and have the time. With that, will even a conventional oil changed often help protect internally the engine seals?