Oil stains on asphalt driveways are not just unsightly—they can get tracked into your house or in your car. Removing oil stains from your asphalt driveway is not at all like wiping up a food spill on your kitchen floor. Instead, you need to adjust your methods and use greater force in combination with chemicals that effectively break up the oil.
Basics of Cleaning Oil From Asphalt Surfaces
Even before you begin, you have an advantage. Asphalt is an impermeable surface—less porous than concrete. Since asphalt sheds water, it also has a tendency to shed oil stains.
You can break up old oil stains from asphalt with force, with chemicals, or with a combination of the two. Force comes in the form of a pressure washer, a nylon scrub brush, or a wire brush. Chemicals are either petroleum-based or they can be environmentally friendly degreasers.
Once you have broken up the oil stain, the residue must be moved off of the asphalt driveway. Leaving the residue in place will only re-stain the driveway after it has dried.
Do-it-yourself pressure washing an asphalt driveway will break up and wash away oil stains. Pressure washing is pure force and it's a force to be reckoned with. Sustained pressure washing with a needle-thin spray will not just break up the oil but potentially can break up the asphalt, as well.
So, hitting the asphalt with just the right force is a delicate balancing act. Pressure washers in the 1,600 psi range or less may not be able to remove the oil stains. You'll need a higher pressure machine in the 3,000 psi range to effectively remove the oil.
Experience and better tools separate do-it-yourself pressure washing from professional work. For cleaning oil stains, professionals will use a special flat surface cleaning head that looks much like a floor buffer.
Water pressure up to 4,000 psi elevates the large cleaning head, delivering up to 8 GPM. Professional pressure washers can remove even the worst oil stains with this tool, all while preserving your driveway. Because the force is not as directed as with a needle-thin spray, there is little danger of breaking up the asphalt.
An alternative to toxic cleaners, green degreasers work on oil stains without harsh chemicals or abrasives. Most green degreasers use alcohol ethoxylates as their active ingredients. Some green degreasers also include citrus for improved cleaning ability and for a pleasant odor.
Green degreasers can be used either at full strength (directly from the bottle) or diluted with water. For oil stains, green degreasers require vigorous scrubbing with a nylon bristle brush. Follow by washing away the residue with water. Several applications may be necessary to fully remove the oil stains from the asphalt.
Oven cleaner already cleans off oil and grease stains in your oven, so how about on your driveway? While oven cleaner definitely falls in the toxic category—it contains lye, ether, ethylene glycol, and other poisonous chemicals—it will break up the oil stains on your driveway.
Spray the oil stain with the oven cleaner and let it foam up and sit for about 15 minutes. Use a wire or nylon brush to scrub the stain, then wash it away.
Bags or buckets of fine granular clay are sold for the purpose of absorbing oil and other fluids on the pavement. Granular clay is most effective on fresh, standing pools of oil. Old, dried oil spots generally will not be cleaned off with absorbent material.
Scoop the granular clay onto the oil spill, then spread it with a broom. Maintain a thickness of 1/2-inch to 1-inch to fully absorb the spill. Once the oil has been absorbed, sweep up the absorbent and dispose of it.
Cat litter absorbs and cleans oil stains from asphalt much like granular clay because it is also based largely on granular clay.
Granular clay and cat litter too can be used preventative measures, prior to oil spills. Just spread out 1/2-inch or more of the product under the location (such as an engine block) where you expect the oil spill to occur.
When using cat litter to clean oil from your asphalt, be sure to use the clay-based litter. Do not use silica gel or biodegradable cat litters made from newspaper, corn, wheat, or pine.
Cat litter offers the advantage of being a quick way to mop up oil spills from asphalt since many households already have cat litter on hand. If you intend to use cat litter over the long-term, switch to the pure granulated clay product. Cat litter is far more expensive than granular clay.
Low-viscosity spray penetrating oils like WD-40 or Liquid Wrench can clean oil stains from asphalt driveways because they are petroleum-based. These products are toxic, so be careful when using them. While they are effective, they are also an expensive method because so much of the product is required.
Baking soda can do almost anything. But is it up to the task of cleaning oil stains from asphalt?
Baking soda has no special chemical properties that break up oil. Simply put, baking soda is a mild abrasive. Combined with water and a scrub brush, baking soda is moderately effective at breaking up those oil stains. Use only a little water in order to make a paste.
Baking soda can also be used as an absorbent, much like granular clay or cat litter. But baking soda's finer grains are more difficult to remove from the asphalt.