How to Get Oil Stains Off an Asphalt Driveway
Oil is one of the few things that genuinely dissolves asphalt, so this is not only cosmetic. Here is what works, what to never put on your driveway, and how to tell a stain from actual damage.
Why oil on asphalt is more than a stain
Asphalt is aggregate held together by a petroleum based binder. Motor oil, transmission fluid, gasoline, and diesel are also petroleum based, and they dissolve that binder. So when oil sits on your driveway, it is not just discoloring the surface, it is softening and breaking down the thing holding the stone together. Left long enough you get a spot that is soft, then a spot where the aggregate comes loose, then a depression or a hole. That is why I tell people to treat a fresh drip as a small emergency rather than a housekeeping problem.
Fresh spill, first ten minutes
Absorb it before it soaks in. Cover the spill with something dry and absorbent: clay cat litter is the classic and it works well, and sawdust, cornmeal, baking soda, or a commercial oil absorbent all do the job. Put it on thick, press it down, and leave it for several hours or overnight so it can pull the oil up out of the surface. Sweep it up and throw it away. Do not hose a fresh oil spill, because water spreads it and drives it deeper. The goal at this stage is to remove oil, not to move it around.
Set-in stains
For a stain that has been there a while, the approach is a degreaser and agitation. Use a dish detergent with real grease cutting power or a purpose made asphalt safe degreaser, apply it with hot water, and scrub with a stiff bristle brush rather than a wire brush. Let it dwell a few minutes so it can work, then rinse. Repeat it. A stain that has been baking in for two summers usually takes several rounds, and honestly it may never come all the way out. What matters more is that you have stopped the oil from continuing to work on the binder.
What to never put on your asphalt
Do not use gasoline, kerosene, diesel, paint thinner, mineral spirits, brake cleaner, or any solvent to clean an oil stain. It sounds intuitive because those things cut grease, and it is genuinely one of the worst things you can do to a driveway. You are dissolving the binder faster than the original spill was. Also be careful with a pressure washer. A wide fan tip from a reasonable distance is fine for rinsing, but a narrow tip held close will cut into the surface and blow the aggregate loose, and on older oxidized asphalt it will strip material. And skip bleach, which does nothing useful here.
When the stain is already damage
Press on the spot with your thumb or the toe of your boot on a warm day. If the surface gives, or if the aggregate is loose and comes up when you brush it, or if there is a soft depression, the oil has gotten past cosmetic and into the material. Cleaning will not bring that back. The fix is to cut out the affected area, rebuild what is under it if needed, and patch it. It is a small repair if caught early and a real one if the soft area has spread and let water into the base underneath.
Oil spots and sealcoating
This trips people up. Sealer does not bond to oil. If you sealcoat over an oily patch, that patch will not take the coating, and you will see it right through the new seal as a bare spot within weeks. Any oil contamination has to be cleaned and treated first, and there are primers made specifically for spotting in oil stains before sealing. If you are having a driveway sealed, point out the oil spots ahead of time so they get prepped rather than coated over. A crew that just sprays past them is not doing the job properly.
Preventing the next one
Fix the leak, which is the only real prevention. Until then, a drip pan under the vehicle costs almost nothing. If a car parks in the same spot and leaves a spot every summer, consider whether that parking position could change. For a work vehicle that always drips, a mat or a designated pad is worth it. And if you are having a driveway built and you know you will be doing oil changes and mechanical work on it, say so. There are ways to build and maintain for that, and it is easier to plan for than to repair around.
Keep reading
Frequently Asked Questions
Yes. Asphalt is aggregate held together by a petroleum based binder, and motor oil, gasoline, and diesel dissolve that binder. Oil left on the surface softens it, loosens the aggregate, and can eventually create a depression or hole. It is structural damage, not only discoloration.
For a fresh spill, cover it with clay cat litter or another dry absorbent, press it in, leave it several hours, then sweep it up. For a set-in stain, apply a grease cutting detergent or an asphalt safe degreaser with hot water, let it dwell, scrub with a stiff bristle brush, and rinse. Repeat as needed.
No. Gasoline, kerosene, diesel, paint thinner, mineral spirits, and brake cleaner all dissolve the asphalt binder and will cause more damage than the original spill. Never use a petroleum solvent to clean asphalt. Use a detergent or purpose made degreaser with hot water instead.
Not successfully. Sealer will not bond to oil, so the contaminated area will show through as a bare spot soon after. Oil spots must be cleaned and, in many cases, treated with a primer made for spotting oil stains before sealcoating. Point out oil spots to your sealcoating crew before work begins.
With care. A wide fan tip at a reasonable distance is fine for rinsing. A narrow tip held close will cut the surface and blast aggregate loose, and on older oxidized asphalt it can strip material. Never rely on high pressure alone to remove oil, because it drives the oil deeper and spreads it.