Quoted from vid1900:
I've got a medium commercial machine.
Don't use butter or regular oil for popping, because the machine takes the oil over 500*F and regular oil will scorch or break down.
Don't use "popcorn oil" from those food service places either, it's greasy junk.
You want real Coconut Oil - it's high temp, healthy stuff.
Add Flavacol to the hot oil for real movie theater taste.
100% +++ Real Coconut Oil with the high temp Flavacol Salt in the cooker and you have movie quality popcorn heaven.