Recently my transmission cooler had to be changed because the oil leaked and went into.the radiator. The radiator too was flushed out of any of the oil I recently got it fixed and the mechanic( family friend ) said to use distilled water in my radiator instead of coolant.

As i read and heard from several people water rust and corrodes the engine, is he wrong or right?

I live in the middle east & the sentra has about 118500 kms on it so far.

Kindly advise should i put water or coolant in the radiator as im in a dilemma

Thanks for the responses