The amount of zinc in diesel oil has been reduced over the last few years
Not in Shell Rotella.
It has actually but is still over 1000 ppm on the last oil analysis I saw. Bobistheoilguy usually has fairly current reports in their heavy duty engine oil forum.
If you really want to know, go to Walmart and buy a quart of Rotella and for comparison, a quart of the store brand 15w40 and then go to a Kenworth or other heavy truck dealer and purchase two oil analysis kits and send in a sample of each. Should cost you about $50 total +/- and then you KNOW what you're getting. Unless you are approaching roller spring pressures, anything in the 1000 ppm will be fine. Chances are the Walmart brand will test as good or better than the Rotella.
Kevin
