Hey guys I need some technical assistance regarding my 3.0 m3 e36. On start when the car is cold she runs and idles perfect. As the oil temperature increases my oil lyt comes on only on idle. It goes off if I give it a slight rev. The car runs perfectly normall . I not sure if the mechanic had not used the oil I supplied him to do a service with . Any ideas as to wat could be wrong ? Could it be the oil pump ?