This question already has an answer here:

Can rich contract (that holds some ethers) use them as a gas when it would like to call other contract?

http://solidity.readthedocs.io/en/latest/control-structures.html gives an example of feed.info.value(10).gas(800)(); and I am not sure if 800 is deducted from originally send gas or from current contract's ethers.

marked as duplicate by eth Aug 17 '16 at 23:25

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.