Oil drips from a leaky car or lawnmower can leave ugly dark stains on your concrete driveway that seem almost impossible to shift. The good news is that with the right approach and a bit of elbow grease, most oil stains — even older ones — can be significantly reduced or removed entirely. Here's what works, and what to watch out for.
Act Fast on Fresh Stains
The sooner you tackle an oil spill, the better. Fresh oil hasn't yet soaked deep into the concrete's pores, so it's far easier to remove.
- Absorb the excess — Cover the spill immediately with an absorbent material. Kitty litter, sawdust, baking soda, or even dry sand all work well. Leave it for at least 30 minutes (longer for larger spills), then sweep it up and dispose of it in your rubbish bin.
- Apply dish soap or degreaser — Squirt a generous amount of household dish soap (a grease-cutting formula works best) directly onto the stain. Work it in with a stiff-bristled brush using circular scrubbing motions.
- Rinse thoroughly — Use a garden hose or, ideally, a pressure washer on a medium setting. Avoid blasting at very close range as this can damage the concrete surface.
- Repeat if needed — One round often isn't enough. Repeat the process two or three times for best results.
Tackling Older or Set-In Stains
Old oil stains that have had time to cure into the concrete need a stronger approach.
Commercial Degreasers
A concrete degreaser is your best friend here. Products designed specifically for concrete are available from Bunnings and Mitre 10. Look for a product labelled as a concrete or driveway degreaser, follow the manufacturer's dilution instructions, and allow adequate dwell time before scrubbing and rinsing.
Poultice Method
For deep-set stains, a poultice draws oil back out of the concrete:
- Mix an absorbent powder (talcum powder, diatomaceous earth, or baking soda) with a solvent such as acetone or mineral turpentine to form a thick paste.
- Spread it over the stain about 10–15 mm thick and cover with plastic wrap, taping down the edges.
- Leave for 24–48 hours, then scrape off and rinse clean.
- This method may need to be repeated for heavily saturated stains.
Pressure Washing
A pressure washer combined with a degreaser is one of the most effective DIY methods. Use a fan-tip nozzle and keep the wand moving to avoid etching the concrete. Many hire shops across NZ rent pressure washers by the day if you don't own one.
Products to Consider
| Method | Best For | Effort Level |
|---|---|---|
| Dish soap + scrubbing | Fresh, small stains | Low |
| Commercial degreaser | Moderate stains | Medium |
| Poultice (powder + solvent) | Deep, old stains | Medium–High |
| Pressure washer + degreaser | Large or widespread stains | Medium |
| Professional grinding/sealing | Severe or permanent staining | Low (DIY effort) |
Safety Tips
- Always wear rubber gloves and eye protection when using degreasers or solvents.
- Work in a well-ventilated area — solvents like acetone produce fumes.
- Never pour used solvents or oily runoff down a stormwater drain. This is illegal under the Resource Management Act and harmful to waterways. Absorb residue and dispose of it as hazardous waste at your local council facility. Check WorkSafe NZ for guidance on safe handling of chemicals.
- Keep children and pets away from the work area until surfaces are fully rinsed and dry.
Sealing Your Driveway Afterwards
Once the stain is removed, consider applying a concrete sealer to protect against future staining. A penetrating sealer fills the pores of the concrete, making it much harder for oil and other contaminants to soak in. BRANZ recommends sealing exterior concrete in NZ's variable climate to extend its lifespan and reduce maintenance. Sealers are available at most hardware stores and come in matte or satin finishes.
Reapply sealer every few years, or as recommended by the product manufacturer, especially in high-traffic areas.
What Won't Work (and What to Avoid)
- Bleach — Not effective on oil and can discolour concrete.
- Wire brushes on sealed or decorative concrete — Can scratch and damage the finish.
- Petrol or diesel as a solvent — Dangerous, flammable, and creates an even bigger environmental problem.
- Ignoring the stain — The longer oil sits, the deeper it penetrates. Don't put it off.
When to Call a Professional
If the staining is extensive, deeply embedded, or your driveway has decorative or exposed-aggregate concrete that you're worried about damaging, it's worth calling in a professional concreter. They have access to industrial-strength degreasers, hot-water pressure washing equipment, and can assess whether grinding, resurfacing, or resealing is the right solution.
A professional can also advise on whether your driveway's condition warrants a full resurface — particularly relevant for older driveways where the concrete has become porous and is absorbing stains readily. You can find qualified, local concreters on tradedirectory.co.nz.