I would like to install a new toilet seat, but the bolts are so old and rusted that they won't turn and I can't get the old seat off. I've put some oil on, but it doesn't seem to be helping much. Are there any better ways to loosen rusted bolts?

Oil is not the right thing to use unless it's penetrating oil or WD-40. If WD-40 doesn't work you may have to resort to cutting them off.

A dremel tool with a cut-off blade should work.

When that happens to me I take a hacksaw blade, wrap a rag around the end for a handle, slide it between the bowl and seat hinge and cut those suckers off. Good luck, Tom