Did you look at your radiator to see it it's oily? There is an oil cooler in there which would have high flow through it, and could also be a "phantom" leak.

Since you say that you've noticed that the oil looks dirty at normal oil change intervals, and has done so for a long time, I suppose that it's possible that yours was always a "loose" engine... simply meaning that all the tolerances of the parts that found their way into your engine during assembly, added up to the greatest allowable clearances, as opposed to the tightest possible fit.

Manufacturers would probably say that at 130K, running well, passing emissions tests, etc. etc... say "thank you" and don't complain. But I think that most Volvo owners, just like you, know that it should do better than that.

Have you tried any of the "high mileage" oil formulations? Or perhaps stepping up a bit in viscosity? Or both? You could try something like a Castrol High Mileage 10W40, and see what happens.

Good luck

Marty
'96 855T