It is a sign that the car has been neglected over the years. Now, it may last for quite a while, or it may go on you next week. it is hard to say. However, with it being a Buick 231 V6, I would probably run 20W-50 oil in it as a precaution due to the rather poor oil pump design that tends to be the Achilles heel of that engine.
For those who think it is just a sign of high mileage, my Nissan pickup with 337,000 miles will not have it's oil go black until it is well over the service interval. However, it has been changed fairly regularly, and I do a flush change every so often as well. What's a flush change? I get the cheapest oil I can find and change just the oil with it. I then drive it for 10-20 miles and change it again. This flushes out all the old oil and keeps everything nice and clean inside.
For those who think it is just a sign of high mileage, my Nissan pickup with 337,000 miles will not have it's oil go black until it is well over the service interval. However, it has been changed fairly regularly, and I do a flush change every so often as well. What's a flush change? I get the cheapest oil I can find and change just the oil with it. I then drive it for 10-20 miles and change it again. This flushes out all the old oil and keeps everything nice and clean inside.
