something thicker then coolent

[cosworth34677]

well heres the problem. i want to use something little thicker then coolent in my little bruder converted excavator. the first thought is oil. but oil will eat up the seals in the pump and valves so im looking for something else. i need something with alot of lubeness(not a real word) im running the pump at a higher voltage then mangom hrc says to 11.1 not the 7.4v. so want to be sure its getting a good lubing.

also one of the clients we have at my work is a cat repair shop and he was saying i would get little more power out of the pump if use a thicker fuild. i don't know how true that is but always looking something other then toxic coolent in my toys.

so any ideas? please reply