u/Sea_Department_1348

Last time I went to the mechanic I told him to replace the coolant. He called me and said it looked ok did I still want him to do it. Of course I told him no(lol). I'm wondering what is the consensus with changing these fluids? I asked about the transmission fluid and he told me no need to drain amd refill just to top it off(and he only charged me like $10 I guess for the little bit of fluid he used)? Can these fluids be inspected or do I need to change them at an interval. Both have been changed once(car has 145k miles) so both sets of fluid have around 100k on them.