It can help reduce oil consumption, smoke, and emissions from older engines. High mileage oil also works to minimize leaks and oil seepage. While you could use high mileage oil in a younger car without harming it, the issues that high mileage oil addresses usually don't appear in vehicles with fewer than 75,000 miles.
Is high mileage oil a gimmick?
If an engine isn't burning or leaking oil, or if it uses, say, less than a quart over 6,000 miles or so, switching to high-mileage oil may not be worth the extra cost for you. ... High-mileage motor oil doesn't hurt and it could prevent leaks from starting.
Is high mileage oil better than synthetic?
High mileage oil is designed for vehicles with more than 75,000 miles. ... This leads to less leakage and oil burn-off, which can be common in older cars. If your vehicle is high-mileage and high performance, it's suggested that you go with this type of synthetic oil. Not every car requires synthetic or high mileage oil.