I have tested them in many engines, and have done butane torch sludge test which these online ordered zic etc don't meet...
When you go and buy stuff for car. Why do people say Japanese de dein? What's the reason behind it?
It is that they want premium parts.
You go at serena and ask for a chicken tikka, when you will have it, either you'll say it's delectable or you'll say its crap. But a sheeda ustaad making a tikka on a rerhi with lots of germs on it would have a lot of quality difference in a premium food.
Now it depends on your pocket which one to eat.. Its your stomach, either your mind will tilt it towards your benefit like yar yei sasta wala kha lo kuch nai hota... Since your mind has taken a decision you'll keep on defending it kay yar kuch nai hua im okay..
So my advice is either use these oils first the premium one's first, see what's the difference.
Don't just write conclusions by eating rerhi wala chicken tikka and concluding yar serena wala to buhat genda hoga yehi sahi hai..
So don't get offended, above examples are not related to you or your personal life. They're just oils and example of quality.