I have been looking for days and can,t for life of me find the zinc level OR if this oil is ok for my 1994-GMC--350?? -flat tappet ] I have been using the 5w-40 diesel oil but want to use a oil for gas engines --Maybe I,ll just keep using the 5w-40 diesel if this 0w-40 is not good? All they keep going to is the 15w-40 diesel OR 15w-40 race oil? Was thinking on there 5w-50 oil it is rated SM so is it ok for street use correct??? but also think its to thick? I use schaeffers products in my 5 mowers --etc. --I use the 15w-40 race oil in my gas mowers and works good from what I can see,,,and like them for those things--- but don,t like to use 5w-30 oil at all--- Also I have three older bolens tractors with eaton-11 hyd. pumps and was thinking on using schaeffer,s #315 hyd. oil in the transmissions for them? Been using 10w-30 synthetic motor oil -----They use this same pump in wheel horse--bolens--cub-cadet etc. and everyone says use something different??? eaton says use 20w hyd. oil but 10w-30 oil is ok too. I have read ALOT post on this subject and looks like if the oil has molly and other friction modifiers it be ok anyways?