I switched to RP from M1 last year on reccomendations from various people,no one here... I have read that rp is not as good as M1..Is this the case??? I run rp in my truck 5.3 and wifes car 3.8...5w30 in the winter ,10w30 in summer...Should I go back to M1 and why??? Can I run 10w30 all year round??? temps range from 0 in winter to 95 in the summer,both are extreme temps and last less than a week...I plan on keeping both for a loooooooooooooooooooong time... Thanks..