I think 2010 was the last year for the V70 so you are thinking of buying another vehicle with a limited dealer network that is at least 8 years old . Forget it . If you have read anything here is that used luxury vehicles are expensive to maintain and that does not seem like anything for you.
I’m thinking that it could be some “coked” residue from the turbocharger that has gotten into the crankcase, and that would not be a good thing.
This is a turbocharged engine? Oh my. Then I’m thinking the same as VDC above. Whatever the source, turbo unit or elsewhere, some kind of carbon/coke deposits have broken loose. Carbon/coke can be differentiated from most plastics b/c It won’t melt at any reasonable temperature. Years ago I had a summer job where I’d have to test the melting point of certain precursors of plastic. What we used was sort of a hot plate equipped with a thermocouple and a microscope. We’d turn the hotplate up and watch when it melted, then we’d note the temperature from the thermocouple. OP could figure out a way to do something like that I suppose.
Not all plastics “melt”. Thermoplastics do melt, thermoset plastics don’t - think bakelite or phenolics. They turn to a crusty burnt product much like the OP describes.
I think that lends credence to yours and @VDCdriver’s “turbo oil coke deposits” theory.
Thanks, although–for the sake of the OP–I hope that I am wrong with that theory.
Here is a possible scenario:
The previous owner changed oil infrequently, “wailed on it”, and did not consistently use the proper specification motor oil, thus leading to “coked” oil in the turbocharger.
Now that the OP has changed the oil 3 or 4 times in 13k miles, using Mobil-1 (NOT “Mobile” 1 ), some of the coked deposits in the turbo have been loosened, and have been washed into the crankcase.