i own a old model cd100.i hv changed my engine oil company,will it affect my milege?

[suvendudebasisn]

I used to put the engine oil herohonda company.
but 2 days back i used servo 4t engine oil.
i m surprised that my bikes mileage has fallen down to nearly 43 from 60-63?
please do suggest on how recover a good mileage.