How to Remove Oil Stains from Your Driveway Before Sealing

Oil stains on concrete driveways are one of the most stubborn exterior cleaning challenges homeowners face. They're also one of the most critical to address correctly before applying driveway sealer — oil trapped under sealer will bleed through, and you'll be left with visible dark patches that look worse than the original stain. Here's the right approach, from fresh spills to years-old stains.

Acting Fast on Fresh Oil Spills

Time is the most important variable in oil stain removal. Fresh oil (spilled within the last 24–48 hours) has not yet fully penetrated the concrete pores and can be significantly removed with the right approach. Oil more than a week old has begun to polymerize — chemically changing in the concrete pores — and becomes dramatically harder to remove.

The moment you notice a fresh oil spill on concrete, here's the correct sequence:

1. Don't add water yet. Water spreads oil and drives it deeper into the pores. Your first step is absorption, not washing.
2. Apply an absorbent material generously to the oil. Best options: cat litter (clumping or non-clumping), baking soda, cornmeal, or commercial oil absorbent (sold at auto parts stores). The absorbent material pulls oil out of the surface pores.
3. Wait. Leave the absorbent on the stain for a minimum of 30 minutes. For a thick spill (fresh oil change drip, for example), leave for 1–2 hours or overnight.
4. Sweep up the absorbent thoroughly. Do not wash it down with water — this re-spreads the absorbed oil.
5. Apply degreaser and proceed with the cleaning steps outlined in the next section.

Baking soda has the advantage of being a mild abrasive and mild alkali in addition to being absorbent — it can help lift some surface oil beyond pure absorption. Cat litter is typically more absorbent for large spills.

For very fresh spills on hot summer concrete (where the oil is still liquid and hasn't begun penetrating), adding a light dusting of Portland cement to the absorbent layer creates an even more aggressive absorption action. This is an old maintenance trick that works well for large fresh spills.

Treating Old, Dried Oil Stains

Old oil stains (weeks to years old) have undergone partial polymerization — the oil molecules have chemically bonded with each other and partially bonded to the mineral structure of the concrete pores. This makes them significantly harder to remove than fresh stains.

Set realistic expectations: a stain that has been in the concrete for years may never fully disappear, even with professional treatment. You can typically achieve 70–90% improvement, but old stains in light-coloured concrete that had significant dwell time may leave a permanent shadow even after treatment. This is important to know before sealing — the sealer will lock in whatever remains.

The treatment process for old stains is more intensive than for fresh ones:

1. Heat the stain if possible. A heat gun or even hot water helps soften polymerized oil and makes it more susceptible to degreaser penetration. Apply heat briefly before the degreaser.
2. Apply a commercial degreaser liberally. Products like Purple Power, Simple Green (the concentrated original formula), Zout, or commercial concrete degreasers are all effective. Apply generously — you want the degreaser to penetrate, not just sit on top.
3. Extend dwell time. Old stains need 20–30 minutes of degreaser contact minimum. For very old stains, consider covering with plastic wrap to prevent the degreaser from evaporating and extending dwell time to 45–60 minutes.
4. Scrub aggressively. A stiff-bristled brush (a deck brush or a heavy-duty scrub brush) worked in circular motions and with the grain of the concrete surface agitates the softened oil out of the pores.
5. Rinse thoroughly with hot water if available, then pressure wash.
6. Repeat if necessary. Multi-generational old stains often require 2–3 treatment cycles to achieve the best possible result.

Degreasers That Work on Concrete

Not all degreasers perform equally on concrete oil stains. Here's a breakdown of common options from most to least effective for old concrete stains:

For the most stubborn stains, a two-step approach can be effective: first treat with a petroleum-based solvent (mineral spirits or WD-40) to loosen the polymerized oil, then immediately follow with an alkaline degreaser (Purple Power, commercial concrete cleaner) to emulsify and lift the loosened oil. The solvent step is particularly effective on asphalt-contamination stains (from tar or asphalt driveways) as well as old motor oil.

Pressure Washing Technique for Oil Stain Removal

After degreaser treatment, pressure washing is the final step to flush the loosened oil out of the concrete pores. Technique matters significantly here:

PSI for oil stain removal: Use 2,500–3,000 PSI for concrete with old oil stains. This is toward the higher end of what's appropriate for concrete and provides the force needed to flush emulsified oil out of the pores after degreaser treatment.

Tip selection: A 15° or 25° tip aimed directly at the stain provides more concentrated cleaning force than a 40° tip. This is one situation where a narrower tip is appropriate — you're concentrating cleaning force on a defined area rather than sweeping over a large surface.

Hot water if available: Hot water pressure washing (also called power washing) is significantly more effective at removing oil than cold water pressure washing. The heat helps re-liquify partially polymerized oil, and the hot water carrying the degreaser solution penetrates the pores more effectively. If you have access to hot water pressure washing equipment (or hire a service that uses it), use it for oil stain removal.

Work inward from the edges: Rather than washing across the stain and potentially spreading oil to clean areas, start from the outer edge of the stain and work toward the centre. This confines the oil rather than spreading it.

Multiple passes: Make several overlapping passes over the stained area. Don't expect one pass to pull all the oil out. Between passes, you can reapply degreaser and scrub again for maximum effect.

Rinse the surrounding area: After treating the stain, rinse the surrounding concrete thoroughly to prevent any emulsified oil (now in the rinse water) from settling into adjacent pores as it dries.

"The most important thing we tell homeowners is: don't seal over an untreated oil stain. The sealer locks the oil in, and within months you'll have dark bleeding patches coming through the sealer in the exact shape of the original stain — but now you have to strip the sealer to fix it."

— David, D&D Home Services Co-Founder

Stains That Won't Fully Remove: Managing Expectations

Some oil stains in concrete are permanent in the sense that no amount of treatment will make them completely invisible. This is particularly true for:

• Multi-year stains that have undergone significant polymerization deep in the concrete
• Stains in light-coloured or white concrete where even a 90% reduction in staining leaves a visible shadow
• Stains in porous or weathered concrete that has significant surface porosity from years of freeze-thaw damage
• Large spills that saturated a large area — there's simply more oil to remove, and some will remain at depth
• Dark oil stains over asphalt — asphalt already contains oil compounds, and differentiation between asphalt and oil staining is limited

For stains that won't fully respond to cleaning, options include:

• Concrete resurfacing: A thin overlay of concrete or polymer concrete overlay can provide a fresh, clean surface. This is more economical than full replacement on an otherwise sound slab.
• Strategic sealing: Apply a darker-toned sealer that minimizes the visibility of remaining staining by reducing the colour contrast.
• Acceptance: If the stain is in a low-visibility area or the remaining staining is minor, sealing over the best-treated surface is sometimes the practical choice — with the understanding that the stain will be slightly visible in the finished sealed surface.

Sealing Over Treated Stains: What You Need to Know

The reason oil stain treatment matters so much before sealing is chemistry: most driveway sealers are petroleum-based (for asphalt) or water-based acrylics (for concrete), and they don't bond well with residual oil. Worse, solvent-based sealers can re-liquify residual oil in the pores and cause it to wick up through the sealer film, creating dark spots and visible bleeding months after sealing.

To verify the surface is ready for sealing after treatment:

• Water bead test: Sprinkle water on the treated area. If it beads up rather than soaking in, residual oil may still be present (or the sealer test indicates the pores are still partially blocked). The concrete should absorb water readily before sealing.
• Visual inspection under different lighting: Check the treated area in bright sun and at a low angle. Remaining oil staining is most visible when the concrete is wet — wet the surface and look for darker areas.
• Allow 48–72 hours after treatment before sealing, even if you think the stain is gone. This allows the degreaser to completely off-gas and any remaining oil to become as stable as possible before sealing locks in the surface.

Our pressure washing service includes oil stain pre-treatment as part of our driveway cleaning process. Combined with our driveway sealing service, we provide a complete solution from stain removal through sealing — ensuring your driveway sealing investment is protected by proper prep.

D&D Home Services TeamExterior Cleaning Experts

D&D Home Services is Kitchener-Waterloo's trusted exterior cleaning company serving Kitchener, Waterloo, Cambridge, and Guelph.