What is the recommended Oil for the CT's ? I've been using Rotella T-4 20/40 in my Mowers and My Classic 1999 GMC Denali since it went out of warranty- 170,000 on the clock and uses 0 oil. I changed the Oil on my 70 CT and used the same Rotella It has above average ZDDP additives. Gas: I've always used NON-Ethanol- 90 Octane in my Mowers for years - I would suspect these vintage 70's Engines would benefit from the same.All of my CT's seem to like it. Thoughts ?