Alloy wheels are a popular alternative to hubcaps on many cars today. They're attractive, and they'll look great for years if properly maintained. Unfortunately, alloy wheels can quickly become dirty and stained from brake dust from the brake calipers, as well as environmental factors like dirt and grease. There are a number of commercial alloy wheel cleaners on the market, but you should always start with mild cleaners like soap and water to get the initial dirt and grime off your wheels.
Mist the wheel lightly with warm, soapy water and clean it with a rag. Get all of the dirt that you can remove off, then mist it again with clean water and dry with a clean rag.
Mix a generic car shampoo with water and sponge off your wheels. Rinse off with clean water.
Consider using a commercial alloy wheel cleaner if soap and water aren't strong enough to have an effect on stains. Read all the directions on the bottles. Apply the cleaner directly to the wheel, then work it in with a clean rag.
Apply a stain-specific cleaner to target fuel stains, oil, silicones, wax, gum, grease, resinous tree sap and adhesive residues.
Rinse the wheel off with clean water once the stain has been removed, and consider applying a car wax or polish once the wheel is dry. A good wax will protect alloy wheels from future staining.