See the effect of a part-payment against your outstanding loan balance.
Works exactly like a one-time prepayment against your current outstanding balance.
Interest saved: Original total interest − new total interest after the part-payment
What's the difference between prepayment and part-payment?
They mean the same thing — paying extra towards your loan, outside your normal EMI. 'Part-payment' is just the more common term used once a loan is already running.