He says "old iron", that could mean anything, but in my personal opinion it's probably for the best to bump up a weight once a car gets over 150k on the odometer. You get a little thicker film to compensate for wear, a bit higher viscosity to cut down on any leakage, and the same low temp performance.

I would not play around with it on anything with VVT, but it's a pretty common "hack" for pre-2010'ish motors and probably even a good idea.