Concrete is tough, but it is also porous. Oil, diesel, hydraulic fluid and tyre residue soak into the surface of car parks, driveways, service station forecourts, warehouse aprons and loading docks, leaving dark stains that ordinary sweeping and hosing will never shift. Those stains make a site look neglected, can create slip hazards and, when washed carelessly, can carry pollutants into stormwater. A purpose-made concrete cleaner and a clear method solve all three problems.
For hydrocarbon stains specifically, a dedicated concrete oil stain remover such as Agar Oil Stain Remover penetrates the pores and lifts oil that general detergents leave behind. This guide covers the main types of concrete soiling, the right product for each and how to clean without breaching environmental rules.
Why Concrete Is Hard to Clean
Unsealed concrete behaves like a hard sponge. Liquids wick into the capillary pores, where oils oxidise and bind to the cement paste. Surface cleaning only removes what is on top, so stains reappear as the surface dries and deeper oil wicks back up. Effective concrete cleaning therefore needs products that penetrate and emulsify, plus enough dwell time and agitation to draw soil out of the pores.
Common Stains and the Right Concrete Cleaner for Each
Oil, Grease and Fuel
The most common problem on car parks and loading docks. Use an alkaline, solvent-boosted or specialised oil stain remover. Fresh spills should be absorbed immediately with an absorbent granule or pad before any liquid cleaning.
Tyre Marks and Rubber Residue
Forklift and vehicle tyre marks respond to heavy-duty alkaline degreasers with machine scrubbing. Non-marking tyres on forklifts reduce the problem indoors.
Efflorescence and Cement Residue
White, powdery efflorescence and cement splatter are mineral deposits and need an acidic concrete cleaner or concrete remover. Acids must be used carefully, pre-wetting the surface and neutralising and rinsing afterwards.
General Grime, Mould and Algae
Shaded, damp areas grow dark algae and mould that become slippery. A general-purpose alkaline concrete cleaner followed by a suitable biocide treatment and pressure washing restores the surface.
Rust Stains
Orange marks from steel furniture, fertilisers or machinery need a specialist rust remover, typically an oxalic or phosphoric acid formula.
How to Remove Oil Stains From Concrete
- Absorb fresh spills with granules or pads and sweep them up for correct disposal.
- Contain the work area. Block or cover nearby stormwater drains before applying any liquid.
- Apply the concrete cleaner or oil stain remover undiluted or at the label ratio, working it into the stain with a stiff broom or deck scrubber.
- Allow dwell time so the product penetrates, keeping the area damp if it starts to dry.
- Agitate again and then rinse with a pressure washer or scrubber-drier, recovering the wastewater.
- Repeat on old stains. Deep, aged oil may need two or three treatments; some permanent shadowing can remain on very old stains.
Environmental Rules: Keep Wash Water Out of the Stormwater
In Victoria, stormwater drains flow directly to creeks, rivers and Port Phillip Bay without treatment. EPA Victoria’s stormwater guidance makes clear that chemicals, oil and other business waste must be kept out of the stormwater system, and businesses can be fined for letting contaminated wash water run off site. When using any concrete cleaner outdoors:
- Use drain covers or bunding and recover wastewater with a wet vacuum or scrubber-drier.
- Dispose of recovered water to sewer only with the relevant trade waste approval, or through a licensed waste contractor.
- Keep spill kits near fuel and oil storage and train staff to use them.
- Choose biodegradable formulations where they will do the job.
Concrete Cleaning in Warehouses and Loading Docks
Inside warehouses and distribution centres, sealed or polished concrete floors need a different approach from rough external concrete: ride-on scrubbers, neutral or mildly alkaline detergents and pH-appropriate products that do not damage sealers. For a broader look at products for these sites, see our guide to warehouse cleaning supplies. On dock plates and external aprons, where diesel and hydraulic leaks are common, keep a concrete cleaner and absorbent on hand for immediate response.
Protecting Concrete After Cleaning
Once clean and fully dry, a penetrating concrete sealer makes future spills far easier to remove, reduces dusting and improves appearance. Reapply sealers according to the manufacturer’s schedule, and use drip trays under parked machinery and at refuelling points.
Choosing a Concrete Cleaner: Buying Checklist
- Soil type: alkaline or solvent products for oil and grease; acid products for efflorescence, cement and mineral stains.
- Surface: check whether the concrete is sealed, coated, polished or exposed aggregate.
- Method: manual scrubbing, pressure washing or machine scrubbing affect the dilution and foaming properties you need.
- Environmental profile: biodegradability and wastewater recovery requirements.
- Safety: read the SDS and supply the right PPE, particularly for acidic concrete removers.
Frequently Asked Questions
What is the best concrete cleaner for oil stains?
A dedicated oil stain remover or solvent-boosted alkaline degreaser works best. Apply, agitate, allow dwell time and rinse with wastewater recovery.
Can pressure washing alone remove oil from concrete?
Pressure washing removes surface grime but rarely removes absorbed oil. Pre-treating with a concrete cleaner is what lifts the oil from the pores.
Is it legal to wash cleaning chemicals into the stormwater drain?
No. In Victoria, only rainwater should enter stormwater drains. Wash water containing detergents, oil or sediment must be contained and disposed of correctly.
Cleaner Concrete, Safer Sites
Choosing the right concrete cleaner for each type of stain, applying it with proper dwell time and agitation, and capturing the wash water keeps car parks, driveways and loading docks presentable, safer and compliant.