It will effect the warranty because its a different oil viscosity that Honda does not recommend. As a dealer Technician, use the oil that the oil cap indicates or look in your owners manual. You definitely wanna use full synthetic ow-20, but putting 5w-20 won't hurt anything, maybe slightly less gas mileage. As far as the 5w-30 idea, I would not put that in your CR-V, it's much more viscous and can cause internal problems down the road. That is my personal opinion and experience in the industry and specifically for Honda's.