Synthetic oil

It won't hurt if you try it, see if you notice a difference. All oil made today whether conventional or synthetic is LIGHT YEARS ahead in chemical design than the oil that was around back when these engines first came out. Synthetic does withstand more abuse (high heat, HP etc.) and can go longer before breaking down like conventional, also is a bit better at reducing friction so frees up a little (barely noticeable) HP/gas mileage.