I don't know about switching to full synthetic with that number of miles on the engine. I've read that it could cause issues due to it being a 'thinner' oil. I'm not sure if that is true with these newer engines or not.
"In fact, some new cars require synthetic oil. However, one exception is with older vehicles, especially those with high mileage. The seals in those engines may not be able to handle the additives in synthetic oil. However, that doesn't mean it's impossible to switch to synthetic in an older car."
Peter
I had heard synthetic oil will actually clean the engine, removing any sludge present. Which is why when changing to synthetic the recommended to make the first 2 oil changes at 3000 miles.
The issue is that sometimes this sludge is what's keeping the seals from leaking. Remove the sludge and expose the leaks
both the royal purple and mobile 1 websites say that this is nonsense heres what I read on another site
wheels.ca/guides/the-long-run-synthetic-oil-in-high-mileage-engines/
Myth, Busted
In the past, a common argument against switching to synthetic oil in an older car was rooted in the belief that a synthetic oil would react poorly with the rubber seals of a high-mileage engine, causing them to break down and spring leaks where none previously existed. This was primarily blamed on the synthetic oil’s viscosity properties, which were said to allow the lubricant to find small holes in the seals and gaskets of an older engine, creating new leaks.
Like all good myths, there may have been a granule or two of truth to that argument years ago. To understand the skinny on today’s synthetic oils, we spoke to Sarah Nordin who works at ExxonMobil.
“This year, we introduced a new high-performance synthetic motor oil, Mobil 1 Extended Performance High Mileage. The new oil is specifically designed for high mileage vehicles with more than 120,000 kilometres on their engines,” explained Nordin. “It is a full synthetic specially formulated to help resist oil breakdown, prevent sludge, and stop leaks in higher mileage engines.” That last point used to be the entire reason
not to use synthetic oil in an older engine, a notion that is now seemingly biffed to the curb like yesterday’s recycling.
In any case I did it.
with mobile 1 high mileage synthetic, My first change was at 3000 miles second will be next week at 5000 and then at 7500 or as suggested by Blackstone labs