I have been using M1 in this engine starting at about 6000 miles.(1 free change from dealer). This engine with slightly more than a year on it has about 37,500 miles on it. We recently got back from a trip to Oregon and back which put 6400 miles on the M1-10w30. Should I change it at 7500 miles or can I take it to 10,000 with no problem? I usually change it at 5000 miles with a new Toyota filter. Thanks guys. Jimmy