I have been using Mobil 1 on my civic but bought some Penzoil Platinum because of the nice comments on this board and that Walmart had it on sale for good price. Any way, I still have about 1.5 liters left of M1 and thinking of using PP for the rest for the next oil change. (The Civic takes 3.2L). Would this be OK? Both the oils are 5W30.