Does anyone know the specific reasons behind this recommendation? I'd like to switch to synthetic and feel that it won't cause any problems but I wish I knew the motivation for Nissan stating against it in the owner's manual.

 

My guess, is that by recommending mineral oil (dino oil), they are removing one more variable from the mixture of possible failure points. Since the engine was tested and tuned on dino oil, by recommending it, they are sure that within normal parameters it will do such or that.

Jim