wrong tranny oil?

[Krakey]

hey guys i replaced my transmission oil a few days ago with some oil that my bro had left over from when he did his. the oil is castrol epx 80w 90. changing gears now especially on cold mornings is rather bad and especially upshifting and downshifting into 2nd. 3rd and 5th are very sloppy and grate slightly when going into gear no matter how softly and smoothly i change. was just wonderig if i have used the wrong oil or is it just because its a t5?

thanks in advance

Krakey