l change the oil at 3000mi intervals, every time l turn the car on it disappears..Under a load the light comes on

Your engine oil pump is going bad! Get a new oil pump!

The oil pressure light only means that the pressure in the oil system is below where it should be.

If the light comes on after hard driving, or with a load like u said, it is not abnormal for it to do so, as long as it turns off after u start up again. If it constantly is turning on & off, u need to check the oil, & if it is low, then add more.

Just make sure the light does not come on while you're driving. If it does, turn off the engine immediately & check the oil. If u don't, u can permanently damage ur engine.

check the oil sender unit. its inexpensive and easy to change

Your best bet is to have someone check the actual pressure with a gauge. Or you can purchase a mechanical gauge, at your auto parts store. Remove the oil light sending unit and screw the gauge adaptor in it is place. If the pressure is good then buy a new sending unit. If the pressure is low you need a new pump or possibly an engine rebuild. Bad main bearings can also cause low oil pressure.

Your engine is going to die. l suspect your oil pump has problems.

Change the oil, and filter. l have seen oil filters cause restrictions on the Lexus V-8 engines before causing this. Otherwise hook up a mechanical guage where the sensor is right above the oil filter on drivers side of engine. See what oil pressure really is and if it is low time to spend some $$. Replace bearings, and oil pump.