I doubt a big establishment just to save a few bucks on oil would be doing something like this. This looks like some hera pheri of the branch employees. Maybe they were showing they are buying oil and then selling it off outside and then replacing that missing that oil with gutter line oil or something along those lines.
Mind you this is not the first time I've seen this in Pakistan few years back people were scavenging same gutter line oil from marriage halls, refining, repacking and selling it off. This was in Karachi.
In any case how can you call yourself a human if you do this kind of shit, even animals don't do this to each other. How morally corrupt and greedy do you have to be to do this kind of shit.