Recently had my 1965 Mustang 289 professionally rebuilt. In order to receive the warranty I had to use either the Rotella 15W40 or Valvoline "Racing Oil" 10W30. This has something to do with modern oils not having Zinc in them. The oils mentioned above has the max. amount of Zinc. I was told to change the oil at 500 miles and then replace with a high Zinc oil. I started with the Rotella & will probably stick with it.
Harold
