Disable Discrete GPU

Hello, I know this has been asked before but I can't find any recent threads talking about this so I figured I would ask for myself.

Anyways, I have a Late 2015 MacBook Pro with the intel i7 4870HQ and AMD R9 M370X discrete GPU. I don't want to have the AMD GPU turned off permanently, but pretty much what I would like to know is if I can disable it for a specific application. For example, I like to lay in bed and play Old School Runescape. Unfortunately, according to Activity Monitor, jagexappletviewer is set to Requires High Perf GPU and it drains the battery crazy fast and also heats up the MacBook a lot more than I want it to. I mean, I am only running Old School Runescape which isn't a demanding game at all and I know the intel integrated graphics can easily handle it, which would help lower power usage and heat.

So if anyone knows of a way I can set it to where that application listed above, is set to run on integrated graphics, that would be amazing and help out so much!