DEX210 rtr diff gear oil

[jesuslovesaloser]

I have just finished a 4 gear mid motor conversion and noticed there was not any oil in the geared diff(2 gear). I used Core RC 450cst shock oil and noticed
the motor was running hot ( after 25 mins on astro turf). I just bought S-works 3000cps diff oil but, I am cautious to use it because it is thicker than the shock oil. Is my logic misplaced and would a thicker oil be better suited?.
Please help.