Hi

Yes lemon oil is recommended for rosewood fretboards, use it to clean and condition the board occasionally, not too often.

Dont use it on maple fretboards. Perhaps the guy was talking about other woods.

My acoustic has another dark wood finish, cant remember what offhand, think lemon oil is recommended for that too.

Fretboard Care
To oil, or not to oil...
One of the questions most often asked in the newsgroups is 'How do I take care of my guitar's wood?' It is also a discussion that is plagued with misinformation and half-truths. This article should clarify many of the misconceptions about fretboard care.

The vast majority of guitar fretboards are made of rosewood, ebony or maple. These are dense woods with different characteristics. Maple fretboards are almost always sealed with a varnish or lacquer coating and require very little care other than cleaning. The sealant coat prevents dirt and grime from getting into the pores of the wood and accumulating.

Rosewood and ebony are left untreated and the natural oils in the wood protect them. The cleaning products that can be safely used on maple are unsuited to these woods. The same care that is used for these would apply to other dense natural finish fretboards (unvarnished).

General rule number one about fretboard care is to avoid any products that contain silicone. While silicone oils are inert substances, problems over the long term will be avoided by not using them.

General rule number two is to avoid products that contain waxes. This includes carnauba, paraffin and silicone waxes. You do not want to apply a waxy residue to the fretboard, you merely want to clean it and leave a very thin oil protectant.

What about furniture care products like "Lemon Pledge"? Aerosol furniture polishes contain waxes, petroleum distillates, emulsifiers (detergents), and lots and lots of water. A very light spray on maple to clean it is fine, but aerosol polishes should not be used on unvarnished fretbaords. We do not want to apply products containing water to the natural finish of a guitar neck and fretboard.

A statement that is seen many times in the newsgroups is "use only 100% lemon oil". First, there are NO furniture care products that actually contain nothing but lemon oil, and even if there were, you would not want to use it on a wood finish. Pure cold-pressed lemon oil is very expensive and could not be marketed for $3 or $4 per bottle like the furniture oils you see in stores.

"But Product XYZ says that it contains 100% lemon oil." Yes, I've seen products with that on the label, and I assure you it is a false and misleading statement. It is used in the context that the product contains 100% lemon oil conditioner as opposed to a cheaper steam-distilled citrus oil or synthetic duplicate made from pine tree wood. Typically 99% or more of the product is a mineral oil with less than 1% lemon oil.

Pure lemon oil (or other citrus oils) is composed of d-limonene at an amount of 90% or more. There are other minor components that give each of the citrus oils its own unique flavors and fragrances. These ingredients include citral, linalool, geraniol, nerol, citronella, pinenes and other terpenes.

Since d-limonene is the majority of lemon oil (or orange oil), we can look at its properties to determine why it is not suited for fretboard care. First, and most importantly, d-limonene is a very strong solvent. It is used to remove glue, paint, grease, oil and other substances. If an oil with a high percentage of d-limonene were applied to a fretboard, it might even begin to loosen the bindings, fret markers or other trim. Additionally, it could soften some varnishes or lacquers used on necks and bodies. Also the vapors of d-limonene are flammable with a flash point of about 124 degrees F.

What are petroleum distillates? The type of petroleum distillates used in furniture cleaners is a very thin, purified and deodorized mineral oil. Normal paraffin and iso-paraffin oils are generally used since they are less agressive to finishes and have lower odors. They are also flammable but the flash points are usually above 200 degrees F.
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I see this question alot - I just don't get why people don't use normal 'ol fretboard conditioner made specifically for - fretboards! Ernie ball sells Fretboard wipes in a plastic 'jar', and in over 2 years I haven't used more then 1. Gibson sells conditioner too in nice little bottles - lasts forever. Martins, Gibsons, Fender rosewoods, PRGs, etc. all look and feel great after using these couple items.

So care for those finishes would be similar to taking care of your car,

Up until recently all I've owned are maple fingerboards and have always used lemon oil on them. I've been doing it like that more than 25 years and have never noticed any problems with it.....unless a super smooth fingerboard is a problem. I've had thickly finished fingerboards and oil finished fingerboards. Never had a problem.
MULLY

Try naptha and a toothbrush. (preferably one you aren't going to use again)

I've used Old English lemon oil for over 20 years with no problems.