I have a 2018 Mazda 3 that just went off warranty. Car only has 28K miles on it. Most of these have been long road trip miles. I have always used QS 0w20 full syn. since new. My 21 Mazda CX5 turbo and older Nissan PU both use 5w30. I've seen numerous threads discussed here that often suggest using 5w30 in lieu of 0w20. I'm thinking of the change purely from the standpoint of having to only keep one weight of oil on hand (planning on sticking with QS as it has has been my favorite for its Mazda loving moly content). Any good reasons why I should not do this? Thanks