I would think Delo or Rotella would be excellent oils for what you describe, but you'll have to watch the viscosities. What you need, really, is just a boost to the basic additive pack of the oil. It seems many of the SM oils have begun using Moly to compensate for the lower levels of extreme-pressure additives, and that by itself is probably enough, especially if you use a well-fortified SM oil like Havoline. If you want extra peace of mind, you could mix in even just a quart or two of a good HDEO oil, or you could use an oil boost additive like Valvoline Synthetic Oil Treatment (VSOT), or if the viscosities were appropriate you could go to a full 15W-40 HDEO like Delo. All are good options. I am running about 50/50 Delo 15W-40 and Havoline 5W-30 in my older BMW right now, which specs very heavy oils generally.
- Glenn