Originally Posted by rmfnla
You are not deforming the hole, you are expanding it. The taper acts as a wedge against the softer aluminum and lubrication accelerates this. BTW, I'm an ME as well; really, don't grease the taper.
How about if Jobst Brandt says grease the taper? He explains in detail why it can't matter. See
http://draco.acs.uci.edu/rbfaq/FAQ/8f.11.html