Whether you’re polishing, sealing, or resurfacing a concrete floor, removing oil and grease properly is absolutely critical. Stains don’t just look ugly — they stop coatings and overlays from bonding, cause delamination, and can permanently ruin finishes. In this guide, we’ll walk you through exactly how to clean oil, grease, and embedded stains from concrete floors the right way, so your projects stay solid, stain-free, and long-lasting.
Start by inspecting the stained areas carefully. Light surface oils are easier to remove. Deeply soaked motor oils, hydraulic fluids, or cooking grease may penetrate several millimeters into the slab. Look for dark stains, water beading (oil repellency), and sticky residues. If the stain is recent, cleanup is faster. If it’s old and deeply embedded, you’ll need multi-stage cleaning. Knowing the contamination depth shapes your removal plan.
If visible pools of oil or grease are present, remove as much as possible before chemical cleaning. Use disposable cloths, absorbent pads, or a scraper to lift thick layers. Do not pressure wash fresh oil — this spreads contamination deeper into concrete pores. Blot carefully and collect waste properly for hazardous disposal if needed (especially automotive or industrial oils). Getting rid of bulk grease upfront makes chemical cleaning faster and more effective.
Use a heavy-duty, alkaline (high pH) degreaser designed for concrete. Avoid acidic cleaners — they can etch concrete and drive oil deeper. Apply degreaser liberally across the stained area using a pump sprayer or mop. Allow it to dwell for 10–20 minutes (per product instructions), keeping the surface wet during this time. Dwell time is critical — it breaks down oils, allowing them to lift out of the pores instead of just smearing across the surface.
After dwell time, agitate the degreased area using stiff brushes or rotary floor scrubbers fitted with aggressive pads. Scrubbing helps emulsify the oil and physically lift it from the pores. Manual brushing works for small spots; mechanical scrubbers are better for larger stains or whole floor areas. Scrub in multiple directions and ensure mechanical pressure is applied evenly across the stain zone for maximum penetration.
After scrubbing, rinse the surface heavily with clean water. Use a wet vacuum or floor squeegee to immediately extract rinse water — never let dirty water just soak back into the concrete. Extraction prevents redepositing oils back into surface pores. Multiple rinse-and-vacuum cycles may be needed for heavy contamination. You’ll know you’re making progress when rinse water stays clear and the surface stops repelling moisture.
If stains persist after degreasing, use a poultice method. Create a thick paste of degreaser mixed with an absorbent material like talc, diatomaceous earth, or sawdust. Apply over the stain, cover with plastic, and allow it to sit for 12–24 hours. The poultice draws oil up from deep within the slab. Once dry, remove the paste and rinse again. Severe old oil stains often need two or more poultice applications to fully lift.
Test cleaned areas by spraying water — properly cleaned concrete will absorb water immediately and evenly. If water beads up or sits on the surface, oil or degreaser residue remains and must be re-cleaned. Only once concrete passes a water absorption test should you proceed with resurfacing, polishing, or sealing. Rushing this step almost guarantees coating failures, bubbling, or discolouration later on.
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