My probably useless 2 cents about oil. A few years ago I bought a pristine 89 Mazda 929, less than 40 K and perfect, owned by the dealership's owner's wife. And it really looked it and ran like it, perfect. (All this is before my MB diesel conversion). Anyway, I thought I'd go synthetic since I wanted the thing to last forever (still have it, 117000 and counting, actually and selling but....). Put in Mobile1 somethingw something, not 0W and it started to leak and leak big time. Before switching to synth I ran dino for 10,000 (changed every 3K) and never had a speck of oil, even underneath the car you had to work pretty hard to get dirty. BIGGEST mistake I ever made. Switching back didn't fix it. I've since been told by Mazda the rear seal is leaking. Now for historical purposes, I have had three of these cars, one went to 275,000 the other is at 205,000 and neither leak oil to speak of, both were always dino oil. I'd use synthetic if the car came with it and the warranty required it but I'll never switch again. The dino's are just as good when changed at 3K intervals, or even 5K in the diesels that hold more oil if they are regularly driven at hiway speeds to heat everything up. Don't switch.