Can you? Yes. When synthetic was first introduced it got a bad rap because people's engines started leaking. If you have any kind of old seals or gaskets the synthetic will find leak points. If it's fresh re-gasket or rebuild then you should be good. Any old/older seals you have the synthetic will find them and leak.

 

Thanks. I think in that case I may use s regular oil. I think the gaskets are somewhat old. Just got the vehicle but I see the oil is pretty dirty. Time for a new oil and filter change. Thanks again.

 

Something that old you want might want to run lead additive in the gas to help protect the valves and and zinc in the oil for other moving parts. I see a lot of guys running Shell Rotella T4 in their old cars. Something to research maybe.
Cool truck too btw
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Lead was for the exhaust seats.