DISCLAIMER: I'm in no way associated with the people who make Oil Eaters and get no financial benefit from posting this. I just like the product.
If you guys haven't already tried it, you might want to think about picking up a bottle/jug of Oil Eaters the next time you are at Costco.
My uncle runs lawnmower repair as a hobby out of his garage and turned me on to this stuff. He uses it to clean engines, linoleum floors, and carpets (the latter items he tries to clean before the wife returns home ).
After my Grandmother died, my uncle and I helped clean her house. The Oil Eaters helped remove black marks from the carpet that the carpet washer couldn't get out. We just sprayed the area, let it soak for a minute, then scrubbed it out a bit with a dishrag - came right out.
For engines or rims, spray it all over the area, let it sit a bit, then hose off. For upholstery, just do the spray and dab up thing.
You can dilute the stuff as well if you need, but I'm no expert in doing that.
Here's a link, note that the price is for TWELVE bottles. I think you can buy it individually inside the store, or get a 1 gallon jug and just refill the bottle (although the 12 bottles is cheaper than the jug).