Hi Scotty, I have a diesel 2018 KIA SORENTO with 70,000 kms with an 8-speed automatic 

I have just had serviced recently and the dealer has found that the transmission fluid is low. (It seems strange that it could be low as it’s not leaking) anyway they have re booked it for a top up . But I’d like them just to change the fluid as it has never been done . They want to use a Castrol ATF SP4 instead of the genuine KIA ATF SP4 because they said the castrol oil is a lot cheaper. Should I be pushing for the genuine fluid or does it not matter?

Also I asked if the filter should be replaced and they said that it doesn’t need to be due to being difficult to access. Is this correct in your opinion? 

Thanks Scotty, I really enjoy your channel Andrew