I have a shorthaired domestic cat she is about 15 years and has mats, even though I comb her, it doesn't seem to do any good.

Is there something I can put on her fur, like some kind of oil, that would help while combing??
What about shaving her, is this the only other answer, can it be done at home?

I appreciate any info you guys can give.............. thanks :)

Combing has to be done on a regular basis to be effective. Some cats need to be combed daily, some every few days. Dead, lose hair is what causes the fur to matt. The Furminator works good to get all the dead hair out. But that would be for after your cat is matt free. If you can't work the matts out with your fingers or with a comb, gently. Then you will probably have to take your cat to a groomer to be shaved. Then you can start a more strict regime of grooming. Baths also help but the cat has to be matt free before bathing or else you'll have even more of a mess. I don't recommend trying to shave the cat yourself. They have a very tissue paper thin layer of skin that is easy to clip and introduce infection. It rips very easily.

Thank you for the advice...I will try to comb out the mats, if that doesn't work, i will go to the groomers or vets.