Bar oil is not just to lubricate. It needs to cool the bar/chain too.
I would say the primary job for it is to absorb heat and as it fly off, take the heat with it.
There is friction on all stuff that cut. Not just from spinning on the bar, but each cutter create heat to as well as friction off the sides.
Rapeseed oil is what I mostly use, my customers too. Easy on the saw, bars, cloths, don't stick even if it sit a couple years.
And probably better for us than any other oil. As we walk thru a mist of bar oil as we cut, that is a factor.