I just bought a 2003 LC w 107000 miles on it. I have a 2000 model with 150000 miles on it. The 2000 model gets 5w30 conventional oil but the previous owner of the 03 used a blended synthetic oil. No problems in the 00 model just wondering if I should change the 03 model and go with the conventional 5w30. Would it start leaking, what should I look for. Is it ok to go back and forth between the 2.