How to lubricate entry doors and what to use : Penetrating Aerosols
Quote from Article entitled How to lubricate entry doors and what to use:
It will be sufficient to lubricate an interior door lock once a year. But as for the entry door, situated outside of the house, it needs to be taken care of more regularly. NB: oiling can sometimes make problems with the lock worse. Metal dust may stick to working parts of the locking-mechanism along with the lubricant, and this can have bad consequences.
The full version of the article can be found here.