Well my amateur understanding is. Low mileage is the potential for problems, including oil. In your car, I would use that 20 50 mineral like wot Mr Volvo approximately specified.
As you mention the filter. I vaguely rem ember an old discussion about oil filters. It might have been something about a valve that is desirable n the filter. I suspect any "quality" filter will do the job well.
Some members will hear me about to say this. My choice I buy a Volvo filter. I do NOT advocate Volvo parts regardless, but it is always worth checking the price and availability. A fair number of members have found it worthwhile to find one of those dealers who do care about parts for older Volvos and "
build a relationship". To find a good dealer for parts I resorted to one hundreds of miles away with excellent service including excellent delivery. They are well aware and understand that I sometimes buy from third party suppliers.
P.S. My local parts shop are well aware and accept that I buy either Volvo parts or parts from the various suppliers specialising in parts for [older] Volvo. The conversation was approximately. Is your car the Volvo 240 that I see in [
name of street]? ...
.