Castrol has a new 20/50 syntec vintage oil with a zinc additive. Here is the oil data and a site where it can be ordered with no tax or delivery charge at $10 a QT. http://www.nemgtr.org/TSO_Pages/200804TSO-Pages/Page34.pdf http://www.proformanceusa.com/mall/castrol_syntec_20w50.aspx Don Queen