Can driveway sealer be applied over oil stains left by my car, or do I need special prep first?

Oil stains must be cleaned and treated before applying driveway sealer, or the sealer will not adhere properly and will peel off within weeks. Fresh oil creates a barrier that prevents sealer from bonding to the asphalt surface, while old oil stains have penetrated into the asphalt and weakened the binder.

For fresh oil spills (less than 24 hours old), immediately cover the spill with cat litter, sawdust, or commercial oil absorbent and let it sit for several hours to soak up the liquid oil. Sweep up the absorbent material, then scrub the area with a stiff brush and dish soap or commercial degreaser. Rinse thoroughly with water and let the area dry completely. For older, set-in stains, you'll need a petroleum-based degreaser or TSP (trisodium phosphate) cleaner. Apply the degreaser, let it sit for 15-20 minutes, scrub vigorously with a stiff brush, then rinse and allow to dry for at least 24 hours before sealing.

Ottawa's freeze-thaw cycles make proper oil stain treatment even more critical because water can penetrate oil-weakened asphalt and cause accelerated cracking through the winter months. Oil stains also attract dirt and debris, creating unsightly dark patches that show through sealer if not properly cleaned. In Ottawa's climate, where sealcoating every 2-3 years is essential maintenance, taking shortcuts on stain preparation means you'll likely need to strip and re-seal those areas within one season.

If oil stains are extensive or deeply penetrated, consider using an oil stain primer specifically designed for asphalt before applying your topcoat sealer. These primers are available at most home improvement stores in Ottawa for $25-40 per gallon and help ensure proper sealer adhesion over treated stain areas. For severe staining where the asphalt has become soft or crumbly, you may need to cut out and patch those sections with cold patch before sealing - though this is temporary repair that should be properly fixed with hot-mix asphalt by a professional.

Test a small area first if you're unsure whether your cleaning was effective. Apply sealer to a 2-foot square section over a treated stain and check after 24 hours - if the sealer looks uniform and hasn't peeled or bubbled, you can proceed with the full application. The key is ensuring the surface is completely clean, dry, and free of any oil residue before sealer application.

Need help finding a driveway contractor for more extensive oil damage repair? Ottawa Driveways can match you with local paving professionals who can assess whether stained areas need patching or replacement before sealing.