PAVEMENT PROBLEMS
Oil Stains Softening Asphalt: Why Drips Damage Pavement
Dark stains under parked vehicles where the pavement feels soft, sticky, or has started to pit and sink.
Why petroleum eats asphalt
Asphalt binder is a petroleum product. Motor oil, gasoline, diesel, transmission fluid, and hydraulic oil are also petroleum products. They dissolve the binder rather than sit on top of it. That is the whole mechanism, and it is why a stain is not just cosmetic.
The progression is predictable. First a dark spot. Then the surface goes soft in warm weather and you can press a thumbnail into it. Then the aggregate loses its grip and the area starts pitting. Eventually a hole forms in the exact footprint of the drip.
Depth of damage depends on how long the fluid sat. A fresh drip cleaned up the same week does very little. A puddle that soaked in over a winter can compromise pavement well below the surface.
Where it happens most
Residential driveways get it under the regular parking spot. Multi-family and commercial lots get it in the same stalls year after year, especially where older vehicles and work trucks park. Any spot where equipment idles or is serviced will show it.
Cold climates add a factor. Vehicles that sit through a long winter drip more, and cold pavement holds the fluid on the surface longer before it soaks in. When the surface warms up in spring, everything that pooled goes into the asphalt at once.
Loaders, plow trucks, and generators are the worst offenders on commercial property up here. Hydraulic fluid is especially aggressive, and a burst line puts a lot of it on the pavement in a hurry.
Can it be sealed over?
Light surface staining on firm pavement can usually be handled. The area gets cleaned and degreased, and a primer or oil spot treatment is applied so the sealer will bond. Skipping that step is why you sometimes see sealcoat that has released in perfect circles under parking spots. Sealer does not stick to oil.
Softened pavement is a different answer. If the material has gone spongy and you can push into it, the binder in that spot is compromised through the depth of the damage. No coating fixes that. The soft material has to be removed and replaced, which is patching, and we do not pave, patch, or overlay.
Sealer family matters for this specific problem. Some sealers resist petroleum better than others, which is one reason parking and equipment areas get treated differently than a residential driveway.
Preventing it
Fix the leak first. Everything else is managing a symptom. On a shared lot, that means talking to residents or tenants about the worst offenders, which is never fun but is cheaper than pavement.
In the meantime, put a drip pan or a piece of cardboard under a known leaker, clean fresh spills promptly with an absorbent before they soak in, and keep the lot sealed so the surface is tighter and less absorbent to begin with. Call (530) 587-4161 and we will look at it and tell you which stains can be treated and sealed.
Keep absorbent on the property before you need it. A bag of oil absorbent in the maintenance shed costs almost nothing and stops a spill from becoming a repair.
Quick answers
Will pressure washing remove an oil stain from asphalt?
It removes surface residue. It does not undo binder damage that has already happened below the surface, and too much pressure on aged asphalt will strip material. Degreasing and rinsing is generally the better approach before sealing.
Does sealcoating protect against future oil drips?
It gives you a barrier and buys time to clean a fresh spill before it reaches the asphalt. It is not immune. A steady leak sitting in the same spot for months will get through eventually.
The sealer peeled in a circle where a car parks. Why?
That is an oil spot that was not fully cleaned and primed before sealing. Sealer cannot bond to a contaminated surface. The fix is proper preparation of those spots at the next application.
More in the pavement guides and the FAQ, or see every pavement problem we get asked about.
Not sure what you are looking at?
Send a photo or call (530) 587-4161. We reply within one business day and we will tell you straight whether it is something we can maintain or something that needs a paving contractor.