What ever you do don't use Renapur, it is thinned with linseed oil and is like vaseline, a friend used it on his leather interior it totally ruined it, not only did it stain the seats everytime you went round a bend or braked you slid off the seats. So you definitely don't want it on your steering wheel. I connalise leather interiors for a living you need to use Gliptone GT15 gentle cleaner to clean the steering wheel and re-colour it, the colour dye has a sealer built in. I have done many steering wheels and they come out as good as new.
Any problems or advice just send me a message and I will be happy to help.