2017 Outback 86000 miles. Mine had the same thing. Didn't know what it was or when it started, just always seemed to be there. Thought it was just a "Subaru thing" as my girlfriend's Toyotas don't do that. About 6 weeks ago, started seeing a cloud of whitish grey smoke from the tailpipe on a cold start. It was just random and I thought it was just condensation. Started happening more frequently. Took it to an independent Subaru mechanic as I don't trust the local dealership. The " oil scraper ring" was clogged with old oil and sludge. I had done 6000 mile oil changes per the manual but sometimes these were done at > 6 month intervals. Did not "top up" the oil levels every 1000 miles as some owners do. Never knew it was an issue and never saw a low oil warning light. Mechanic said he was seeing this oil scraper ring problem more often in newer cars (did not specify if this was just Subarus). He thinks manufacturers may have changed the composition and or design of the rings. Had the top of the engine rebuilt (valve grind, new rings etc) for $4K. FYI, I'm retired, most of my driving is local stop and go traffic which may have contributed to the problem. Per his advice, will top up the oil every 1000 miles, full oil change every 3K miles and take it out frequently for some freeway driving. And the rattling noise on start up is gone.
