Yeah, there was always a gal at the barn that recommended doing that. If anything it won't hurt to try it. I know they did it to a couple of the barn cats, and it seemed to work well, I think it only had to be done once or twice a year [since they were all outdoor].My grandmother told me about the babyoil for earmites, and I guess if it's safe for babies it's gotta be safe for kitties. But if your worried you can cal your vet and ask. I have done this for years and it works, with no side effects.
I only do it when I see the brown in their ears, or excessive wax. I use a syringe, to get it past ear fur, lol. I only use 3 drops MAX, then I hold the ear down and gently rub to get the oil in good. The cats to the rest by shaking their heads, after the cat I am treating shakes it's head I take a cotton ball and very gently remove the gunk (you have to be very careful, ears are very sensitive.) Then I let the kitty shake it's head more and remove more of the gunk until it's clean. For very extreme cases I put the drops in wipe out the gunk, let the cat shake it's head remove more gunk, add 2 more drops, remove more gunk, etc.
I've used Acarexx in the past for some of the barn cats and it worked like a charm in two applications.
Are you guys sure it's ear mites, and not just wax build up due to a possible food allergy, or simply a cat having a constant ear problem? I only ask because it may not be ear mites at all. The kitten I adopted had "earmites" I'm pretty sure the woman didn't look under a scope because most kittens from bad situations have them and his ears were dirty, but as it turned out he was itching his ears.