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...this topic has engendered spirited discussion on bicycle forums ever since I started reading them, long ago.
I used to install them dry, and attempt to torque them to specs, then retorque after riding some miles.
Now, I grease lightly, and tighten them down as hard as I can with a Campy BB wrench, which by it's short handle arm, limits the torque you can apply. I've not noticed a difference.
Here's a link to the page discussion over on the Sheldon Brown website:
https://www.sheldonbrown.com/brandt/...ng-cranks.html
A lot of the Jobst Brandt quotes come from his old discussion board , where there was a long back and forth on this. It's another example of bicycle mythology, like much of the chain lube discussion hereabouts.
Because friction plays no role in torque transmission, preload in the press fit must be great enough to prevent elastic separation between the crank and spindle under torque and bending. This means that no gap should open between crank and spindle facets under forceful pedaling. Crank bore failure occurs when the press fit is loose enough that a gap opens between spindle and crank. Torque is transmitted by both the leading and the trailing half of each facet, contact pressure increasing and decreasing respectively. In the event of lift-off, the entire force bears only on the leading edge of facets and causes plastic deformation, causing the bore to take on a "pincushion" shape (loose crank syndrome). Subsequent tightening of the retaining screw cannot correct this because neither the retaining bolt nor crank is strong enough to re-establish the square bore.
The claim that a greased spindle will enlarge the bore of a crank and ultimately reduce chainwheel clearance is also specious, because the crank cannot operate in a plastic stress level that would soon split the crank in use. However, increased engagement depth (hole enlargement) may occur without lubricant, because installation friction could ream the hole.
With or without lubricant, in use, cranks will make metal-to-metal contact with the spindle, causing fretting erosion of the steel spindle for all but the lightest riders. Lubricating the spindle for assembly assures a predictable press fit for a given torque. Without lubrication, the press is unknown, and galling (aluminum transfer to the steel spindle) may occur during assembly. After substantial use, spindle facets may show rouge and erosion from aluminum oxide from the crank, showing that lubricant was displaced.
You really ought to read the whole thing, over on the website, because it's interesting on this topic.