I have a 1988 90 Q with 177K miles. It's been burning quite a bit of oil latley, and I notice that oilly residue is apparent around two spark plugs, and one plug has a Lot of carbon/oil burned onto it. Do you think it could be piston rings or valve seals. With a compression test, could you tell the difference?

 

if oil on the grove then valve seals, if oil on the elecrtode then rings. also you can check by flooring the gas pedal and seaing what smoke comes out. if blue it the beggining then valve seals, if later then rings. if black mixture is too reach, white you have a leak of antifriess into the ignition chember.