Steve Lusardi wrote:
Karl the clearances are much tighter on today's engine. Oil pressure is the
indicator of "potential" flow, but it's all about flow. If the viscosity is
too high, flow will be reduced, because when there is enough pressure to
lift the ball from the seat in the regulator, that will represent an easier
path and pump flow will be directed through the regulator and not the rest
of the engine. Use the viscosity the factory recommended. They built the
engine, not your son.

I agree with Steve. In the short term you'll probably get away with it.
In the longer term you might not. Not worth the risk in my view.

Best wishes,

Chris