I have a 1997 Mazda Protege with 102k miles. for the first 80k miles I was using dino oil at 3000 to 4000 mile drain intervals. I switched to mobil 1 for two changes at 5500 intervals and finally to walmart supertech full synthetic for the last 2 changes. However, all this was before discovering this board. I do not like the fact supertech is a group III oil, and I think synthetics are overkill for my economy car. I've read a lot of good things about Chevron Supreme on this board. The 1.08 price tag at walmart makes it attractive. WHat do you guys think of doing a change with Chevron 10w30 and a Mazda OEM oil filter given that I have used synthetics in the recent past?