[embee]

Agree with YC there.

In production environments fasteners are kept dry to avoid contamination, dirt, faulty assembly, possible H&S issues (dermatitis etc), and in vehicles which have to meet evaporative loss hydrocarbon standards you don't want oily things exposed (even mould release agents on tyres is a problem for this). Consistency of build is most important.

The downside is a tendency for corrosion to get in there in service. There are specs of surface treatments which will give high levels of protection, but it all costs.

I once did some tests comparing torque/tension on some particular fasteners we were having issues with using different surface treatments, and YC's guide for oiled and Loctited applications are pretty much right from what I recall.

Production fasteners needing thread-lock usually use patches of micro-encapsulated material, which is dry as supplied and is controllable (common on disc bolts etc).

General purpose fasteners typically are designed for around 80% of yield, so there is a little leeway in practice. Only things like con-rods, main-bearings and cylinder head bolts are designed to work at yield (in order to control clamp loads achieved), and have specific tightening procedures given (electronic yield sensing or torque+angle methods) and limited re-use.