How to Remove Mechanical Grease from Concrete
Always test on a hidden area first. Never mix cleaning chemicals — bleach and ammonia, or bleach and acids (including many bathroom/vinegar-based cleaners), release toxic gas. Follow the product label on every cleaner you use.
Before you start
- Don't pressure-wash a fresh grease spill on unsealed concrete as a first response — high pressure can drive oil deeper into the pores rather than lifting it out.
- A poultice treatment needs real dwell time (24-48 hours) to draw penetrated oil back out; a quick scrub-and-rinse doesn't reach oil that's already soaked below the surface.
At a Glance
- Difficulty
- Hard
- Primary method
- Absorbent powder, degreaser scrub, poultice for penetrated stains
- Water temperature
- Cool
- Machine washable?
- No
- Success outlook
- Moderate to poor on unsealed concrete; grease that's soaked in is often permanent
What You'll Need
- Cat litter or cornstarch (absorbent powder)
- A concrete-specific degreaser
- A stiff push broom or scrub brush
- Materials for a poultice (absorbent powder mixed with a solvent degreaser) for penetrated stains
- A garden hose for rinsing
Step-by-Step
- Cover the fresh spill immediately with cat litter, cornstarch, or another absorbent powder, pressing it gently into the stain to maximize contact.
- Let it sit for several hours, or overnight for a substantial spill, then sweep up the saturated powder.
- Scrub the area with a concrete-specific degreaser and a stiff brush, working it into the surface texture.
- Rinse thoroughly with a hose, directing runoff away from any drain, garden, or planted area.
- For a stain that's already penetrated unsealed concrete, mix absorbent powder with a solvent degreaser into a thick paste (a poultice), spread it over the stain, cover with plastic, and let sit for 24-48 hours before scraping off and rinsing.
- Repeat the poultice step if needed for a deeply set stain, and accept that some old, penetrated stains will leave a lasting shadow.
Cold Water vs Hot Water
Cool water is used for rinsing, though water temperature plays a smaller role here than the degreaser and poultice steps do — concrete's porosity, not water temperature, is what determines how deep the oil has traveled and how aggressive the treatment needs to be.
If the Stain Has Already Dried or Set In
Grease that's had time to soak into unsealed concrete is one of the more genuinely difficult pairs in this entire matrix, since concrete's porous structure lets oil travel below the surface in a way that plain scrubbing can't reach. A poultice — absorbent powder combined with a solvent degreaser, left to draw the oil back out over a day or two — is the standard tool for this, and even then, an old, deeply penetrated garage-floor stain often leaves a permanent dark shadow that no amount of additional treatment fully removes.
What Not to Do on This Surface
Don't rely on scrubbing alone for a stain that's had time to soak in — surface scrubbing only addresses grease sitting on top of the concrete, while penetrated oil needs a poultice treatment that actively draws it back out through the same porous structure that let it in. Don't use a pressure washer as your first response to a fresh spill, since high pressure can actually drive oil deeper into unsealed concrete's pores rather than removing it.
When to Call a Professional
A professional concrete cleaning or sealing service is worth considering for a large, old, or deeply penetrated grease stain, particularly on a garage floor or driveway with years of accumulated staining, since commercial-grade degreasers and extraction equipment can reach oil that a home poultice sometimes can't fully draw out.
The Full Picture
Concrete's porosity makes it uniquely vulnerable to grease among the hard surfaces in this matrix, since unsealed concrete isn't just resistant to cleaning the way carpet padding is — it actively absorbs oil into its own pore structure the way a sponge would, given enough time.
This is why the standard scrub-and-rinse approach that works for most stains on hard surfaces is often insufficient here — surface cleaning addresses only the grease sitting on top, while a poultice treatment is specifically designed to draw oil that's already penetrated back out through the same pores it went in through.
Sealed or coated concrete (garage floor epoxy, for instance) behaves much more like a hard nonporous surface against grease, resisting absorption well, which is part of why sealing a concrete floor is such a common preventive step in spaces where oil spills are routine.
Old, unsealed garage or driveway concrete with years of accumulated grease staining is one of the more honest 'often permanent' pairs in this whole matrix — a poultice can meaningfully lighten even a deep stain, but full removal isn't always achievable once oil has thoroughly soaked into the material, which is worth knowing before investing significant effort in a stain that's been there for years.
Frequently Asked Questions
- Why won't scrubbing alone remove an old grease stain from my garage floor?
- Unsealed concrete is porous and absorbs oil below the visible surface over time, so surface scrubbing only addresses what's sitting on top. A poultice — absorbent powder mixed with a solvent degreaser, left to sit for a day or two — is designed to draw penetrated oil back out through the same pores.
- Is it ever worth sealing my garage floor to prevent grease stains?
- Yes — sealed or coated concrete resists oil absorption much like a hard nonporous surface, which is why sealing is a common and effective preventive step in garages, workshops, and other spaces where oil spills happen regularly.
- Will an old grease stain on my driveway ever fully come out?
- Sometimes not completely, honestly — a deeply penetrated, years-old stain on unsealed concrete can leave a lasting shadow even after a proper poultice treatment, since some oil may have traveled deeper than the poultice can fully reach.
Surface caution: acid etching on decorative/sealed concrete; prolonged staining once it penetrates the pores.