hi stuey,sorry to take so long to get back,i have been flat out with chrismas car dramas.the cars with he noisy motors were running at the time,not just started.i dont know exactly what causes it but hey i think the lack of oil would be a good place to start.just changing to puflux fixed it,one of the other local parts guys in s.a. tells me the same story he has heard from his customers. stuart.