I think it was esso xd3? 0w40 ci4 rating. Now I just stick to m1 0w40 fs in everything as I'm no longer worried about the 47 year old stock camshaft in my Oldsmobile v8.Growing up on the farm we used Delo 15w40. Lately, dad uses Mobil Delvac. What was the first HDEO you folks used?