An awful lot depends on how one is going to use their blades. But, for me, a little bit of patina goes a long way. I haven't been in the habit of oiling my carbon steel blades at all, but I do make sure to keep them clean & dry. I wipe them down with a little Windex on a clean paper towel or tissue every evening. Isopropyl alcohol also works well in this regard. Either will remove the oils from fingerprints, and Windex (regular kind) also has a little bit of ammonia, which will also help to neutralize acids (from foods, especially fruits). Acids, salts, moisture are what make rust on steel, so keeping these things off your blade makes most of the difference, whether by oiling or not. If you do oil the blade, make sure the steel is clean underneath it. Otherwise, the oil can trap dirt, moisture and anything else against the steel, and make matters even worse.
Just in the little bit of tinkering I've done with 'forcing' patina, I've noticed when the steel was initially clean (little/no patina), some fruit juice or vinegar will produce some red rust pretty quickly, within an hour or less. However, once the red rust is cleaned away (baking soda scrub works well), the grey patina makes a difference the next time around, when again exposed to the same treatment. A 'grey' patina'd blade seems to turn more black with additional exposure, as opposed to making red rust again. The 'black' oxide doesn't harm the steel in the way the red rust does (which corrodes, pits the steel), and it does actually seem to protect it somewhat, based on what I've seen (also confirms all of the testimonials I've read here, about the value of a patina on a steel blade).
I haven't tried A.G.'s RustFree, but the description of it indicates it's a silicone-based product, which seems like it might resist moisture better than oil (mineral oil). Don't know if there are additional ingredients in it which might enhance it's abilities beyond that. I'd think that even at the price of it, a little bit should go a very long way, so it might not seem so expensive in the long run. Especially if it works as advertised (and A.G. has always been good about keeping his customers happy, one way or another. :thumbup
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David
