Vic Correnti (2/23/2009)
I read an article that said the Rotella diesel oil was probably NOT the best choice for gas engines since it was designed for the lower RPM diesels. I'm sure if I look hard enough that I could find an opposite opinion. Ted, do you have an opinion on this? Vic. You asked so here’s my thoughts on diesel oil being used in gasoline engines. I don’t use it in any shape, form, or fashion in this manner simply due to the high level of detergent and the scrubbing action that particular detergent has on bearings and cylinder walls on a gasoline engine. This wear doesn’t happen overnight but when tearing down a multitude of these engines and comparing wear attributes when using known oils, the differences in wear is significant and especially on the bearings.
The SM API rating has been discussed heavily in the past and essentially any SM oil with over 30W in its weight classification does still have the SJ amounts of zinc/phosphorus present meaning it’s still good for the older vehicles without the use of additives. For this reason, most engines leaving the shop are supplied with 10W-40 oil with the recommendation to stay on this particular weight of oil. I’m in Texas so I can get away with this in the winter months.
As Jim (57fairlanepost) mentions, typing in ZDDP in the search bar located at top of the page will bring up past discussions on the subject and some excellent information regarding modern oils. Here are links to all three pages of just one thread in particular.
http://forums.y-blocksforever.com/Topic9285-1.aspx
http://forums.y-blocksforever.com/Topic9285-2.aspx
http://forums.y-blocksforever.com/Topic9285-3.aspx

Lorena, Texas (South of Waco)