I dont plan on putting additives in the transmission. Only additive I used was in my daily that Royal Purple coolant additive which worked great but not for the cost of it. Only additive I use now is putting some marvel mystery oil in the gas tank every so many fill ups.

 

Dady always said dont mix oils.
Trany fluid is an oil.
Do you mix 20-50W with 5-30W? I dont.

 

hmmmm you could mix them it shouldnt hurt considering 20w50 and 5w30 is a multi grade weight (gets thinner when cold and thickens when hot). Personally I wouldnt mix but you could get by puttig 10w30 in a engine that you got 5w30 or 0w30 in and it shouldnt hurt.

My concern is I rather use what is called for. I heard Type F replaced Type A and thought they were identical.