Those Mobil MSDS forms are indeed interesting. M1 10w30 and 0w40 appear to be pure PAO, Delvac 1 and M1 5w50 appear to be a PAO / Ester mix. Also, M1 0w40 in the MSDS is a little thinner (centistrokes) than in the spec sheets (71 and 13.5 in the MSDS v 80 / 14.3 in the product specs).