Can driveway sealer be applied over oil stains left by a previous owner in my Ottawa driveway?

Driveway sealer will not properly adhere over oil stains and will peel, bubble, or wear off prematurely in those areas. Oil creates a barrier that prevents the sealer from bonding to the asphalt surface, leading to patchy coverage and early failure.

You need to remove or neutralize the oil stains before applying sealer to get proper adhesion and uniform coverage. Fresh oil stains (less than a few months old) can often be cleaned with a commercial degreaser, dish soap, or even cat litter to absorb the oil followed by scrubbing with a stiff brush. For older, set-in stains that have penetrated deep into the asphalt, complete removal becomes much more difficult.

For stubborn oil stains in Ottawa driveways, try these approaches in order of intensity. Start with a commercial asphalt degreaser (available at Canadian Tire or Home Depot) applied according to manufacturer instructions, then scrub with a stiff brush and rinse thoroughly. If that fails, try a paste made from powdered laundry detergent and hot water, let it sit for 30 minutes, then scrub and rinse. For the most persistent stains, muriatic acid (diluted according to instructions) can be effective, but use extreme caution with proper ventilation and protective equipment.

If the oil stains won't come out completely, you have two options before sealing. First, you can apply an oil stain primer specifically designed for asphalt surfaces - these products encapsulate the oil and provide a bondable surface for sealer. Second, for large or numerous stains, consider having those sections milled out and patched with fresh hot-mix asphalt before sealing the entire driveway.

Ottawa's freeze-thaw cycles make proper sealer adhesion even more critical than in milder climates. Sealer that doesn't bond properly will crack and peel during winter expansion and contraction, creating an unsightly mess that's harder to fix than starting over. The oil-stained areas will also collect water and salt, accelerating deterioration of the underlying asphalt.

When to hire a professional: If you have extensive oil staining or the stains cover more than 10-15% of your driveway surface, consider having a paving contractor assess whether spot repairs or full resurfacing makes more sense than attempting to clean and seal over the damage. Professional contractors have access to stronger degreasers and can determine if the oil has penetrated so deeply that surface cleaning won't be effective.

Need help finding a driveway contractor for stain assessment or repairs? Ottawa Driveways can match you with local professionals who understand how to properly prep oil-stained surfaces for long-lasting results.