You will get a lot of opinions here. I have used Castrol for 20 years or so. When I realized it really wasn't green anymore I was not that interested like I was. I have been using Pennzoil and Castrol in my 69 Z for 5 years now but next oil change and from here on out I am using Rotella T. I really don't like additives so I think Rotella is the right oil. Diesel oil always had better lubricant properties in it. I have over 140,000 on my 1998 GMC pickup and always ran Castrol or Pennzoil every 4000 miles. I use a quart about every 2000 miles depends on my driving. (10W40) So who really
But I bought Rotella T for the next Z/28 change.