I know this has been beat to death on this site; but how do you tell the german stuff from the American stuff? Some how after reading all the info on this site, I still don't know. K-mart in my area has syntec 0w-30 on clearance for $3.00 a quart; it looks like old stock, but I don't know. (0w-30 is not a popular weight in this area.) Also can I run 0w-30 in a 91 mazda miata? or is it too thin?