I have a 2000 Sienna with 80K miles that has a slight oil leak at head cover gasket. Also a 1997 Camry 4 with 105K miles with no leaks but had engine rebuilt at 60K miles. Both engines call for 5W-30 oil and I just want to get my oil by the case from now on.
I am considering the high mileage oil by Valvoline or another name brand. Is this something that will harm the engines in any way and is there really any benefit towards using it?