Hey, I have a 93 kx 80. Everyone of my friends is telling me to use some Bel-Ray 80w case oil. But the Manual says to use SAE class 10w40 as the "transmission oil". I know the tranny oil gets used for the gears and everything, cause there is only one spot to put oil in, not 2. So, should I listen to the manual, or do what the internet / friends tell me. Thanks.