[Yo-Yo]

Not an expert on motor starter caps, but I do know that another important parameter to a cap, besides capacitance value and working voltage, is current capability.

I believe the oil filled caps are capable of dissipating much more heat from high current flows than a Mylar cap of the same capacitance and working voltage rating.

[Paul R.]

I believe the oil filled caps are capable of dissipating much more heat from high current flows than a Mylar cap of the same capacitance and working voltage rating.

Interesting. I'll have to look into that. However, I do know polyester and PP are often spec'd as "run caps". I'd think if the ESR (internal resistance) is low enough, reasonable current should not be a problem. Of course, some of the tradeoffs are capacity, working voltage, ESR, and size. If capacity and voltage are set, then you have ESR vs. size (essentially)...