I recently switched a high mileage car (2002 Lexus ES300, 228k miles) from dino to M1 HM, 5w-30. This is after the 1st 1k miles on M1HM. This is the Toyota 1MZ-FE V6 3.0/3.3L used in many, many Toyota/Lexus engine 1995-2005. I find it interesting because this is a bit dirtier than the previous Pennzoil dino oil looked at 5k miles at the last change. So my interpretation is that the M1HM is cleaning up deposits that the prior dino oils wouldn't get at. Does that sounds correct? Also, it was my intention to leave it in 7,500 miles. However, should I use a shorter OCI for the first one or two OCIs with the new synthetic oil? The engine seems to love this oil; it could be my imagination but it seems to be (even) quieter, smoother and more responsive than before - and it ran very, very nicely before.