Which cleaning solution do you use in you RCM?

I second Topoxforddoc's solution.
I use very similar 'DIY juice' also. It works as well as any of the multitude of 'magic potions'. I did try a number of them, not that they are bad --- but no better either, then my own mixed stuff. Long live marketing...
Axel

I've consistently had the most superior results from Walker Audio Prelude recording cleaning fluids. I've found the Walker Audio Prelude better than Disc Doctor, RRL, and L'Art du Son which I've used. Disc Doctor made a significant improvement over the DIY formula described above that I'd used for many years, but the Walker Audio Prelude is even better. Others here like Audio Intelligent, but my vote goes for the Prelude four step regimen.
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I agree with Topo and Axel's mix. I even go a little stronger, but it leaves things a little "squeaky". (Is bright clean? I don't know) I also use Audio Intelligent, which, being enzyme based, makes me think it's a little cleaner, as it's getting to release agents and other possible organic stuff like fungus. AI is clearly smoother sounding. No, I don't have my system in a room where fungus is growing...

One of these cleaners is more correct. I don't know which. They definitely sound different. I do know which one costs more: ) Photoflo actually put a warning on its bottle years ago not to use it as a surfactant for anything but photos. I've used it for years and have a pretty nice front end: things still sound great on my analogue stuff. I think I would know from years of use if I were doing any harm to my albums.

Hell, I even use Torumat, which has some sort of lubricant in it. George of Stanalog and AJVDH give a wink and a nod to Torumat. It wins the static contest over my other two cleaners: far fewer static issues and records stay clean while they play, instead of attracting dust with every rotation.

Nobody that I'm aware of has done a significant study on the use of alcohol based cleaners: we know they strip vinyl stabilizers, but no one has agreed at what % and at what rate and therefore, how much is too much.

Labratory grade alcohol? No, I use Everclear 20%, 80% triple distilled ionized water and 2 drops photoflow per 8 ounces. If I'm not using near 100% alcohol, then I want to know what adulterants it has in it. Everclear is pretty free of extra "stuff".

With any alcohol, I have never gone stronger than 1/5 by volume, esp. if I were driving;)

Window Cleaning fluid from my car.
Works well and is cheap

I agree with Rushton and I add MoFi enzyme to the list as a second when I am in a hurry or on new. The walker is a time consuming process but does a great job. I just get some headphones and listen while I scrub and 10 or so records to make the mixing worth while.