The 6015 Series, 6030 Series, 7130 and 7230 Tractors are equipped with a PC (pressure compensated) hydraulic system. This PC system is flowing hydraulic oil whenever the engine is running. Flow will increase with higher engine speeds. If no hydraulic functions are being used, flow returns at low pressure back to the transmission case. When a hydraulic function is used, the pressure required to move the equipment shuts the flow off from returning to sump and it is directed to the hydraulic function requiring oil.
If the SCV levers are not neutralized or left in a detent position after implement movement stops the pressure stays high, causing return oil to pass an unloading valve at high pressure. This causes heat in the hydraulic system and over time will cause a hydraulic oil temperature light to come on.