Before the coat
How do I get oil stains off my driveway?
Oil stains have to be scrubbed out with a degreaser and rinsed before any sealer goes down, because nothing bonds over oil.
The numbers
- Oil, gas and transmission fluid all attack the binder that holds asphalt together.
- Sealer does not stick to a surface with oil still in it. It peels there in patches.
- A fresh spill is a cleaning job. An old one that has softened the asphalt is a repair.
- Kitty litter or a dry absorbent first, then degreaser, then a hard rinse.
Why oil is worse on asphalt than on concrete
Concrete is stone held together with cement, and oil stains it. Asphalt is stone held together with a petroleum binder, and oil dissolves it. A stain on a drive is not only a mark, it is the surface being softened from the top down.
Left long enough the asphalt in that spot goes spongy, then crumbles, and it is a cut out and patch rather than a wash.
The order that works
Soak up anything still wet with cat litter or a dry absorbent and sweep it up. Then scrub the spot with a degreaser made for pavement and a stiff brush, and rinse it hard. Bad spots take a second round. Follow the manufacturer's label on whatever you use, for the dwell time, the rinsing and the handling.
Give it a day to dry all the way through before anything goes over it. Sealer over a damp spot has the same bonding problem as sealer over an oily one.
What happens on a sealcoating job
Oil spots get treated as part of the preparation, and the badly soaked ones get an oil spot primer so the coat has something to hold on to. That is why the cleaning takes longer than the coating on most drives.
It is also worth pointing out the spots when you get the quote. A drip under where a vehicle parks is easy to walk past on a gray surface and impossible to miss once it is the one patch of sealer that peeled.