I assume my motor was broke in on OMC oil. I have no idea what the dealer put in there when they rigged it to go home. As soon as the reservoir got low it was filled with Pensoil 100% synthetic. It only had a couple gallons of that run trough it. That is what I was told buy the original owner when I bought it in 01 with 62 hours on the motor.

When I took ownership I let the reservoir get low. I have ran Amsoil HP injector every since I took ownership. The motor now has 500 plus hours and I have had zero issues with Amsoil

If you had a motor that was under warranty I would use XD-100 it is a 100% synthetic oil. No warranty Amsoil Hp Injector I pay $23 a gallon and Amsoil is 100% synthetic.

Your 99 Evinrude is a Direct Injection motor. Most people will agree that they do preform well on XD 50 which is a 50/50 blend of conventional oil and synthetic oil. If you want the best oil go with a 100% synthetic like XD 100 or Amsoil HP Injector