I have an 05 Corolla XRS with 188k miles (I'm org. owner & always used syn oil, appox. 5k-7k OCI ). I just returned QSUD jugs and bought M1 EP 5w-30. I drive about 15k mi/year now, mainly hwy, rarely stop/go. My plan is an OCI 1x year. Also, I'll finally do a UOA around 10k mi to see how the oil...