It can be restored, and it's relatively easy, but very messy. Use leather prep from furniture clinic with an abrasive pad (take the wheel off first, you will not believe the mess) to remove all the melted leather coating. You'll then be left with a smooth but faded steering wheel, apply some dark grey leather recolouring balm a few times and it will look like new. About £30 and a couple of hours work all in. Best part is that if you remove all the leather coating it won't re-occur, and the wheel feels much better to handle. I did mine 2 years ago, and just need to reapply a bit of balm now and again to keep it perfect.