Interesting quote from the Shell "Tech Expert" from their Rotella Forum :
"Rotella T 15W-40 meets the engine oil performance requirements but not the catalytic convertor chemical compatability"
I had suspected this might be the case, but I had never seen it confirmed before. No doubt, too much phosphorus is the problem. Question is, does the same situation apply to other heavy duty diesel oils which are sometimes used in gas cars? I know a lot of folks use the Chevron Delo product in their gas cars. A few are probably using Delvac 1 or Shell 5W-40 synthetic as well.
There are some other interesting discussions on there also, for example a discussion on base stocks. If you read some of the postings, a few of the "members" appear to be company shills, but interesting reading anyway.
http://www.rotella.com/forum.html