At my last oil change, almost 6k ago, I switched from a dino 5w30 to M1 5w30. Would it be a good or bad idea to use M1 10w30 in the summer and go back to using 5w30 in the winter?
No problem at all, I used to switch back and forth between 5w30 Mobil 1 in winter and 10w30 Mobil 1 in summer myself. My father still does this in his car too.
We have seen really good posts for the 10W-30. I have been using the 10W-30 Amsoil and Mobil for 10 years in Pa all year round. Starts right up in -20F with vehicle outside. I wouldn't even consider 5W-30 in Ga.