Oiling Gut Strings
From Daniel Larson's Gamut Strings Web Page
The question often arises as to whether or not gut strings should be oiled in an effort to preserve them and protect them from wear. In my experience, this depends very much on the individual needs of the musician.
You should consider oiling the strings if:
Otherwise, it might not be necessary to oil strings.
If you do decide to oil your strings, we recommend a light nut oil such as almond oil. This is available in most grocery stores as it is used as a salad oil. It has a neutral pH, which is important for strings, as gut degrades when exposed to base and acid solutions. You will want to use the oil sparingly, and be sure to keep it off of the instrument varnish.
Musicians using a bow will need to be careful to keep the oil away from the area of the string that comes in contact with the bow, as the oil might coat the bow hair and cause it to slip on the strings.