Synthetic oil used to be PAO, polyalphaolefin, or an ester. Now, it is a Group III dino oil, with possibly some real synthetics blended in. Nobody really knows what is in "synthetic" oil these days except the oil companies and anybody who wants run lab tests on it to determine what it really is cuz they won't tell you what's in it. The bottom line is that "synthetic" oil is nothing like it used to be, maybe better, maybe worse, who knows?