SMC TH-16 16" Oscillating Desk Fan | Initial Checkout

The initial checkout of an SMC 16" oscillating desk fan model TH-16. The unit is dated 9/98 and 1/99, making it likely to have been sold during the summer of 1999. It was made in China by Shell Electric Manufacturing Company Limited.
There existed quite a few variations of this fan through the 90s/2000s. This particular head was available in box tabletop and pedestal versions. Each were available in a 12" form factor as well.
There is much debate regarding the differences between the two sizes of these units. Years ago, I remember reading a lot of reports of the 16" model being extremely underpowered and failing prematurely. There were some people who claimed it used the same motor as the 12" model, but with a higher value capacitor.
I have another one of these which seems to be reasonably powerful. This one however, does not. I could see this one using the same motor. I have noticed this same difference in the 16" pedestal version as well, one of the ones I have is reasonably powerful, and one of them seems particularly weak.
I need to perform a full clean and service on all 4, then compare them all side by side including a teardown to finally solve this mystery. There's definitely an inconsistency with these fans, I'm just not sure what it is.