Here's my two cents.
Most cleaning agents use ammonia (or any of its derivatives) as main ingredient mixed with some kind of wax or soap. MC is a good example. I think Pledge is also an ammonia based cleaning agent. And of course, the most popular ammonia-based cleaner of all of them is Windex. The strong smell of MC is ammonia. Check the label of your cleaner.
Is ammonia good for guitars? Here's my fearless opinion - yes and no. Ammonia is an aromatic compound. In small concentrations, ammonia is an excellent cleaning agent because it can remove light grease quickly. But ammonia may fade the tint/color of your guitar finish so be sure to wipe it off quickly. If the finish of your guitar is urethane or lacquer based, i think ammonia is safe to use. But to be sure, wipe it off quickly. Remember Murphy's Law. NEVER use ammonia-based or alcohol-based cleaning agents on old/vintage guitars - many of these guitars have shellac or special mix of varnish coatings that might be dissolved by these strong agents.
Can you use ammonia sold in Mercury? I haven't tried it. But you can experiment by diluting it. Start with an old furniture, on an obscure part.
How about household ammonia? Also known as Ammonium Hydroxide, I think you can use it but dilute it first. Household ammonia sold over the counter has around 5% to 10% concentration of ammonia. Still, when experimenting dilute it further first. It may be illegal to possess large quantities of Ammonium Hydroxide because it is used to produce methamphetamines (crack, shabu, etc.). Experiment on the proportions suitable to your needs. By the way, inhaling ammonia can cause dizziness an can be lethal if in high concentrations. It can trigger asthma attacks. So don't sniff MC and don't pick your nose after applying MC.
Is MC just as good as Pledge? Or should I ask, is Pledge just as good as MC? No comment.
For waxing, carnauba or carnuba wax is a very tough wax and is good even for leather. It can give your guitar that extra coat of protection. It repels water and other liquids effectively. It's easy to apply but it is tough to remove. Dirt/Stain under a carnauba wax is difficult to remove.
Is car wax good for guitars? I don't know and I don't want to try, even the carnauba types. Car paints are designed to be tough. Guitar coating/paint is selected and applied taking into consideration the resonating properties of paints and coatings. I think car wax is too tough for guitars. I don't know.
What about necks and fretboards? For bare wood (fretboard) cleaning, I do not think ammonia-based cleaners will do.
So, what do I use for cleaning my guitars? I use an extra soft baby diaper (not the disposable types) dampened with distilled water (car battery water). Fresh tap water is hard water with chlorine (bleaching agent). I don't know if washable nappies are still being sold in department stores but I got mine long time ago. I just take the time to do that extra wiping for both the body and neck/fretboard, although any kind of soft cloth will do for the fretboard. No wax or oil. Since any kind of liquid will seep through the grains of wood, I dread using any kind of oil/wax because they do not evaporate like water. But I use fine coconut oil (home made clear) on my rosewood fretboards from time to time (once a year or maybe longer) to keep it from being parched.
Just my opinion...
