This is actually true. I used to work for SpaceX and the engineers always used a drop of oil/grease on nuts and bolts. It helps for install and removal and surprisingly actually acts as a mild thread lock once torqued down. I don't know how exactly it works but they did enough testing to prove it! That being said, its still fine to keep the lugs dry, afterall, our trucks aren't leaving the atmosphere very often.

 

I watched a goon at a local NTB tire store crank down on some lug nuts on a van with a 3/4" drive impact, then go over the nuts with a torque wench.
I went up to the front counter and specifically told them that if this goon was the one who was going to put my tires on, I'd just cancel the job and go elsewhere. When the Manager asked me why, I told him what i saw. The reply I got was that the impact gun is what actually does the tightening and the torque wrench is just a double check.... .....I left the store to find a place that knew what they were doing.

 

Bolt stretch is what actually retains a fastener. Specs are often given as torque values, as measuring the torque is often much easier/quicker than measuring stretch. The amount of stretch generated by a given amount of torque is greatly effected by lubrication used on the threads. That's why you'll see different torque values given by companies like ARP based on what lubricant you use on the fastener (motor oil, fastener assembly lube, etc.).