Quote:
Originally Posted by aerobod
A given tightening torque for a dry thread and oiled thread will produce a different strain and consequent clamping force in a bolt. In the context of an oil drain plug bolt, I’d expect the tightening torque would be specified for an oiled thread.
Engine oil increases bolt strain by about 1/3 compared with a dry thread. An M12 8.8 drain plug bolt into aluminium at 20mm thread depth can take a torque of about 60Nm dry or about 45Nm oiled, so a BMW standard torque for an oil drain plug of 25Nm is well within the safety tolerance.
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Well I guess you learn something new every day. I believe OP is referring to the oil cartridge, not the drain plug but I don't think that really changes anything for purposes of this discussion.
I thought that once the contact of the clamp side of a washer/bolt/etc met the surface it was mating to, that is where the torque measurement would begin, and as long as the mating surface has no oil, oil on the threads would not have an impact on clamping torque. I get that the torque to start threading would be different but having trouble understanding why the clamped torque would change.