what engine oil does a 1992 subaru liberty auto stationwagon need? Answers in "w" units please i need to add oil and I cannot find a good reference as to what to use - the oil at the garages are 20 /50 w etc and i have no idea what to use

What engine oil does a 1992 Subaru Liberty auto station wagon need? Answers in "W" units please.

I need to add oil and I cannot find a good reference as to what to use - the oil at the garages are 20w/50 w etc and I have no idea what to use.