The blue on the older Mini's and most all of Rugers older rifles seems to me to be of a better quality then what they are doing today. Anyways, on most all my blued guns I have got away from using oil on the exterior and have been using classic paste car wax.
About the only time my guns get a wipe down with breakfree or an oily rag is in the field if they are getting wet or need a wipe off.
I have been using wax for years and never had any rust on guns in use or stored.
Nevada, The last free place in this country.