I think it depends how you are going to use the car now. What I would not recommend is changing to some expensive fully synthetic oil now - that would be a recipe for oil leaks. If you are going to use it as a daily driver then it would be a good idea to carry on using the same as the PO, which was probably a semi-synthetic 10W40 or something similar. As long as you change it every 10,000 miles the brand doesn't matter much (in my opinion, I'm sure someone will say you have to buy some expensive brand...), so I'd suggest buying whatever Asda or Tesco has on sale.
If you are going to do very few miles in the car - perhaps it is going to be a hobby or project car and so drive 2-3,000 miles/year you might consider doing the same as I have with the Royal Barge and going back to a 20W50 mineral oil, which is probably what it left Gothenburg with in the sump. I've found 20W50 to be very good for an older car (the RB is 40) - but then I change it every 2-3,000 miles:
https://www.volvoforums.org.uk/showp...&postcount=888
The RB neither leaks or burns any oil using 20W50 (it had a slight weep from the rear crank seal when I got it (the PO had used 10W40 semi-synthetic)). 20W50 mineral oil is as cheap as chips (I think I bought 3 gallons of Comma oil for about £17 in someone's sale so I have enough to last until 2023).
Just my thoughts - enjoy your motor car.
Alan