Only for cleaning
Another user was a little bit more irritated. He stated that “WD” stands for “Water Displacement,” and it isn’t intended to be used as engine oil in reality. It’s designed to be used instead of regular engine oil to “clean the individual components of the engine during installation.”
Another comment claims that perhaps WD-40 was never intended to be used as engine oil in the first place, and we have yet another interesting viewpoint on the issue, this one citing that maybe it wasn’t.