What does 'high mileage' oil actually do?

High-mileage formulas such as Valvoline MaxLife and Mobil 1 High Mileage add seal conditioners and additives intended to reduce leaks and oil consumption in engines past roughly 75,000 miles. Verified-purchase reviewers with older vehicles report fewer drips and quieter operation, though these are anecdotal and not backed by independent lab data in our source set.