The best thing would be to call the previous owner and ask what he has been running. There is a risk of switching to synthetic on high mileage engines. Varnish develops over time inside the engine when using petroleum based oils. Running synthetics tend to dissolve the varnish. This can cause oil leaks.
Wow. Most folks move to synthetic oil these days. Likely the previous owner did as well. I would suggest going to synthetic. There are several threads on this site discussion which oil to use. There are several opinions out there. I have been using Repsol.
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