Esso XD-3 0W-30 and GC 0W-30 are similar synthetic oils - both primarily PAO, HD oils that meet the cold-crank specs for a '0W' oil (less than 6200cp @-35C). They are both failry thick, being 'around' 70cst @40C; and 12cst @100C. One thing that has been said, but not entirely 'proven' about these oils is that they most likely DON'T use VII's - they are straight-weight PAO's that meet the '0W' spec. Amsoil ACD is also a primarily PAO, HD oil, but it is thinner - about 66 [email protected] 40C, and only 10.5cst @100C. It 'only' meets the cold-crank specs for a '10W' oil (less than 7000cp @-25C). It is stated by Amsoil that this oil is VI-free. If the Amsoil ACD has a similar make-up to XD-3 and GC, and is actually thinner, shouldn't it ALSO be able to meet the specs of a '0W' as well, not just a '10W' oil?