Oh I am sure there are more suitable parts than the LM358, i was just trying to explain that what he is trying to do is far harder work that using what he already has to do something better. He wants to drop up to 1V on the shunt resistor, 1.5V on 18V does not require too much of a loss in that range. The circuit he has posted already has a current shunt amplifier. To be honest i am confused as to what he is trying to do here.