I did the first transmission oil change at just under 500 mile on my adv 5 Northstar. When I pulled the plug, the oil was black. Only oil I see that black is from a diesel engine . The plug had some material on it. Nothing big or shiny. Looked more like fine powder. So is this a normal color for the oil out of the transmission? I've done two oil changes on the motor and the oil still looks brown. I'm not sure what's inside a utv transmission but I'm a little concerned with the black oil. Or is this just normal for first oil change?