Just read the thread about synthetic oil in Subaru’s . It is said high mileage oil should be used in an engine with over 75,000 miles . What’s everyone’s opinion on that ? All my engines have over 75,000 .
A lot of “high mileage” oil is marketing hype. But, I’d follow the recommended oil as per the owner’s manual.
It’s the oil sellers that say that. That oil swells rubber seals, so if you’re leaking a bit of oil, maybe, but it’s not usually needed.
The son’s 2.5L Jeep engine had a rear main seal that leaked oil. He started using Valvoline High Mileage oil. After driving it fifty miles the oil leak completely stopped.
Then at the next oil change he put in regular oil and the seal leak returned after a short period of time. He drained oil and added the VHM oil and the leak stopped again. So he always used the VHM oil in the engine thereafter and it never leaked again.
So they can stop some seal leaks.
We’ve owned many vehicles with well over 200 and 300 and even 400 thousand miles…never used the high mileage oils…All hype at a higher cost.
If you have leaky seals it can help and definitely does not hurt except slight cost difference.