i have an 07 2.0mzr cd and seems to be runing rough like jumping while idle, when its cold there is no light but as the car heats up while it is idling there is an oil light which can flicker by pressing the clutch and depressing it. I have changed the sensor, it only worsend the problem. There is a whiteish smoke comming from the oil refil cap but the oil is black as it should be with a diesel. There is new oil, filter, air filter and everything that comes with a small service. I dont know if this is connected but as the light is about to light up there is like a heat surge in the cabin from the heater i dont know how to explain it. I would appreciate a little help since in my place there is little to no mazda mechanics. I have bought the car second-hand so i dont really know what was happening before. I did the service a week after i bought the car and then the problems started(i've put 5-30 oil) so i am assuming the previous owner has had additives in the oil that hid the problems enough for sale

 

You will need someone with a mechanical oil pressure gauge to accurately measure your oil pressure.