Well, I just went looking for my Blade Wash can to see if there was a label, but came up empty.  Kerosene and mineral oil is probably right, judging by the smell, which is not totally unpleasant.

I've never clipped my horse with the big clippers, but plan to give it a whirl this year.  I also used to clip dogs, so that's what the clippers were for.  Definitely buy the blade wash, it's a must, your blades will be better for it.  I also had a "blade caddy" with slots for holding the blades, and I used to keep some blade wash in it so they blades were permanently stored in it.  When I needed one, I took the blade apart, wiped it clean and added a small dot of oil, and voila!  However, I also used the Kool Lube, and I think it's great, as blades do get hot, and they run better with a shot of that stuff.  Spray it on while the clippers are running, and you can hear the difference.  I never noticed the blades dulling particularly fast because of it, but I also had back up blades I could switch too.

I'd recommend washing the blades between horses, at the very least.

For storing blades it's good to use oil soaked rags and wrap your blades up then insert into plastic bags.  This keeps the blades from rusting and breaking teeth by banging into each other.  (Writing the blade size on the baggie helps too)

As for blade wash, I use a lubricant and disinfectant found at Sally beauty supply in a small bowl.  I also use an old paintbrush to help get hair out of the blades and a quick blast of air from the compressor.

Here is a product similar to what I use but I can't seem to find it at Sally's now.  Get the jar and just dunk!

http://www.petagree.net/ord_clippers_maint_wahl_h42.html

Here's what I use H-42 and it's mucho cheaper than Oster products and lasts forever.

http://www.norvabarbersupply.com/disinfectants_lubricants_sanitizers.php