What we like about the 100% actual pressed lemon oil is that it contains heavy turpines. These are very similar to the heavy turpines (which are large molecules) that evaporate long after the water evaporates. When you condition with the lemon oil, some of these big molecules get stuck in those cells and help the cells below stay protected from the turpine evaporation. You only need a few drops of the lemon oil once in a while. It helps protect the fingerboard from cracks.
If you don't like lemon oil, or are sensitive to it, it's fine to use other oils - in most cases they won't hurt things. The ones with wax leave things dirty for a while, the ones with petroleum distillates will help clean things up, but they are stinky! Tung oil tends to remain tacky even after years (not everyone experiences this). I'm not big on linseed oil, but others love it. Our esteemed Paul (TBO) used olive oil with great success.
Keep in mind that 99% of our fingerboards are Ebony, and the lemon oil recommendation is for Ebony.
I have heard from a friend that instruments with plastic binding don't like lemon oil (or most oils). He had a Les Paul that he bought used from someone that used Olde English lemon oil (not much lemon oil in it) in a slathering application almost every month. The fingerboard eventually delaminated. Now, I'm not 100% certain the oil caused this, but it's the one case I personally know of that had a bad outcome. But, anything used to excess is never a good idea. Like I mentioned, you only need a scant application of the lemon oil to be effective.
Frankly, if you are actually oiling your fingerboard with anything you're miles ahead of most people in the area of guitar care, and I thank you for that!
