With 130k miles,
The M103 engines were weak on Valve guides. I don't know when a change in materials was made- maybe your 89 has them. They are also weak with headgaskets.
I would go to about 700 miles/quart and start saving up some bucks. If you DIY the head, I suspect the cost could be 200-300 for parts and machine work. I've drilled out the guides and installed new ones by chilling. Worked like a charm and the lapped the guides. But, on a better day, I would install the guides and take it to a machineshop for cleaning up the valve seats.
My 86 model is going to be in the same boat soon. It's got 75,000. I was thinking that excessive oil consumption might lead to an earlier cat failure.
01 vw A4 TDI
66 Chevy Corsa
68 GMC V6 w/oD