The wheel covers attached to a car come into contact with particularly heavy dirt. However, so that you don't have to resort to expensive extra products, oven spray will also do the trick:
Cleaning hubcaps with oven spray
Oven spray dissolves even stubborn dirt like gear oil. After spraying, simply wipe off with water as usual.
Photo by Sabine, meinhaushalt.at
Read also: Removing Fly Dirt from the Car