Yea, I know this is one of those can of worms type question, but today’s diesels have that pesky particulate filter which requires a low SAP oil.   The wife’s car is out of warranty so I’ll be changing the oil, and buying it.   What’s a good oil to use?  Price isn’t an issue since she doesn’t put too many miles on the car.  I’ll probably be changing oil once every 10 months or so

Is this a VW or ???

Mobil 1 ESP was legit when I had a TDI.

The most important thing is to change it at regular intervals, and I will tell you right now, 10months is too long. DPFs and such put a lot of demand on the engine oil, higher EGTS, the turbos work harder and you get more fuel dilution due to how smaller engines regen the filters (inject extra fuel at the cylinder, rather than after the turbo like bigger engines). You can use the best oil but any extended interval will result in deposits and dirty burning that will plug a filter. In my diesel I Run CAT DEO (mostly because I work for CAT so its cheap) but this stuff is awesome. My Cummins was run on DELO for years and I never had any issues but since I work in a CAT shop now I started buying CAT oil because of cost and how easy it is to get. Well after 7K miles of running the CAT stuff the engines internals are cleaner and a valve train tick has gone away, also the engine seems to run smoother. If you cant get the CAT stuff or its too expensive a close second would be Mobil Delvac (Mobile makes the CAT stuff but to a more stringent spec). Also make sure you filter is up to the task too, if its not an OE filter, the bottom end for me is Wix/ Napa Gold. If you can find em Donaldsons are the best filter on the open market.
ETA: if you want to find out where your ideal/maximum change interval is, pull oil samples and monitor them.

Guys thanks for the response.   Dill, I don’t think that oil is low sap.   Through some research, I find mobil 1esp 5w30 seems to the best with a very low sap content which would be beneficial for the dpf.    It’s pricey though at about 11$ per liter.   But I’ll go with it.   Normally, the wife’s car is under warranty and the dealer changes the oil every 10k and I’ve been doing it with dealer oil and filter in between at 5k so it gets 5k oil changes.  I did send one sample off to blackstone and they said it could have gone to 7k or so.  I was wanting to use some exotic oil to feel all warm and fuzzy inside, but mobil 1 is a great oil and I’ll just use that one

Good on ya for following MFG. recommendations, that will keep you out of a lot of trouble. And keep following the recommendations based off of oil samples. These two things will save you TONS of money in the long run.
ETA: Im not 100% sure if the CAT stuff will meet light duty requirements for SAPS, but it is low ash to be after treatment friendly. I will also say from servicing DPFs that I usually only see lots of ash build up if the truck has an extended oil change interval, or if regens have been interrupted or inhibited. But again things could be different on light duty stuff, and it is NEVER a bad idea to follow the recommendations of the OEM.