>From what I can find, these are both non-synthetic (conventional oils). What I cannot find is the ZDDP and Moly content difference. The VV211 is about $5.00 a quart and the VV851 is about $10.00 a quart. The VV851 is "Not Street Legal" whereas the VV211 is "Extreme Performance Level Protection" "with ZDDP". Thanks. Tim Murphy TR4 #317