I'm confused as to which oil I should run in it and whether it needs special oil with high ZDDP because it's a flat tappet engine. The engine is a brand new remanufactured engine from ATK, 3514bbl Windsor so I want it to have the best stuff possible. The only high performance synthetic I can find with ZDDP is Amsoil ZRod oil. I know the EPA has pressured oil companies to cut down on ZDDP levels to protect catalytic converters, this car never came with those atrocities so I'm not worried about harming any emissions equipment! I was hoping I could run something like Pennzoil Platinum 10w30 but can't find any info on zinc levels in that oil anywhere. I really like the looks of Pennzoil synthetics but don't want something that will harm my engine either. What should I use? There are ZDDP additives you can buy but they are pretty spendy, I'd rather just buy an oil with high levels of ZDDP, seems cheaper in the long run. I'd have no problem ordering Amsoil either but want to see what my other options are. Thank you! Will be considering a synthetic oil for the 351 Windsor in my old Bronco as well.