Hi.
Just read your question and had a spare 2 cents. I recently cleaned a steering wheel that had built up sweat and other gunk from the PO over the years. Most cleaners would not touch it including Simple Green. A lesser problem would probably have been fine for Simple Green but this stuff was greasy and caked into the grain.
I tried Meguiars' Mirror Glaze #39 Heavy Duty Vinyl Cleaner with a soft brush and in 1 application the wheel looked like new. I followed with Mirror Glaze #40 Vinyl & Rubber Cleaner Conditioner for a great finish.
You can learn more and see the products on my website at
www.drdetailforless.com
Thanx for listening