valves clattering 300E

MY valves have started to clatter on my 90 300E (2.6). I use regular 10w-40 oil and have the oil changed about every 4,000 miles. The car has close to 150K miles.

Does anyone have an idea on how to quiet the valves down? What would happen if I started using Mobil 1?

I have a 91 ranger that has used Mobil 1 since day 2. It has over 200k miles on it and it is very quiet. Many other people on the ranger site complain about valve noise and the solution is to change to Mobil 1. Has anyone had success with the change to Mobil 1 on a car with high miles?