Are there any bad effects when switching from a "moly" oil such as castrol GTX to a "non-moly" oil such as chevron supreme? I have one car that has had castrol GTX in it for at least the last 50,000 miles (buick V6), would switching over to chevron supreme be a bad idea? I'm wondering if higher mileage engines need the benefits of moly more or less that lower mileage engines? Thoughts?