So, I ended up speaking to both Johnson & owers and Atlantich DDA/MTU. Both said 15/40 MTU oil which I did put in. Same thing goes in the ZF gears. In the future, I think I'll be just fine using Rotella 15/40
The Florida Detroit Diesel Rep here told me not to use Rotella as he's seen engines with excessive piston ring wear on yachts that have used it. This was when we did the engine survey/seatrial for the extended warranty plan on a set of 2006 MTU series 60's. Take it for what it's worth.
I'm a fan of Amsoil too but Yanmar didn't want synthetics at all (1999) so I went with the best non synthetic according to Amsoil tests. Mobil Delvac 1300 15-40 was a step above all the other diesel oils.
Hi, This is the basis for CAT DEO, I remember when it first came out that the CAT Synthetic Oil Spec Sheet was an exact copy of a Mobil 1 Spec sheet with any reference to Mobil by name replaced with the CAT blurb.
Here is MTU "Fluids and Lubricants Specification" information. They list the specifications for all fluids to be used in MTU series (except Series 1800) and DDC S60 Marine. They name the approved oils by a quality category. Category 1 being the lowest to category 3 being the highest. http://www.mtu-online.com/fileadmin/fm-dam/mtu-global/pdf/valuecare/A001061_33E.pdf
