instead of buying cheap buy an Oil which can last 100~300 hours and it will be 100~200RS expensive and generator would be happy too.
I use kixx for 200hours and i usually buy a 5 liter Gallon (more money saving) ... as I have tested this oil lasts upto 2500km in CD70 in brutle abuse type usage so I have no worries if it slips to 225 hours in generator on gas as well..
the generator we have is 2.5KW Chinese OHV Type.