Oil is a tough enemy in the trenches of stain warfare, especially once it has soaked in good and deep. Fresh spills come up with an absorbent and some patience, but if you want to remove old oil stains from concrete, you need a cleaner that breaks the oil down and a method that pulls it back out of the pores.
Here’s how to tackle stubborn stains on garage floors, driveways and walkways.
Why old oil stains are so stubborn
Concrete looks solid, but it’s full of tiny pores. When oil sits on it, those pores wick it below the surface. Scrubbing the top only reaches the oil that’s left up there; the rest stays trapped and can even “wick” back up after you’ve cleaned.
The trick is to re-dissolve that oil and give it somewhere better to go, like a towel or poultice that draws it upward.
Gather your supplies
- TSP (trisodium phosphate) or a TSP substitute, or a commercial concrete degreaser
- A bucket and measuring cup
- Old towels or rags you can throw away
- A stiff nylon scrub brush (not wire, which can scratch)
- Plastic sheeting and tape (for the poultice method)
- Absorbent such as clay cat litter or diatomaceous earth
- Chemical-resistant gloves and safety glasses
- A garden hose
How to remove old oil stains from concrete, step by step
Method 1: The TSP towel soak
This is the secret weapon from our original tip, and it still works.
- Sweep and pre-clean. Remove dirt and loose debris, and soak up any surface oil with cat litter first.
- Mix the solution. Combine one part TSP with four parts warm water, following the package directions. Always add powder to water, not the other way around.
- Soak a towel. Saturate an old towel in the solution and lay it flat over the stain.
- Let it sit. Leave it for several hours. Keep the towel damp by adding more solution as needed.
- Scrub occasionally. From time to time, lift the towel and work the solution into the stain with a stiff brush, then lay the towel back down. The best results come from the towel slowly leaching the stain out.
- Rinse well. Remove the towel, scrub once more and rinse thoroughly with water.
Even if this doesn’t completely remove a deep stain, it will lighten it noticeably. Repeat as needed.
Method 2: The poultice
For the deepest stains, a poultice gives the oil more time to migrate out.
- Mix TSP solution or a concrete degreaser with an absorbent like cat litter or diatomaceous earth until you have a paste about the consistency of peanut butter.
- Spread it about a quarter-inch thick over the stain, extending an inch past the edges.
- Cover with plastic sheeting and tape the edges to slow drying.
- Leave it for 24 to 48 hours.
- Remove the plastic and let the paste dry completely. As it dries, it pulls oil up.
- Scrape and sweep it up, then scrub and rinse the area.
A spot of trouble: quick fixes for grease spots
For smaller or less stubborn grease spots, try one of these:
- Concentrated detergent suds: Scrub hard with a very stiff brush, then hose it down.
- Powdered dishwasher detergent: Dampen the concrete, sprinkle the powder over the spot and let it stand for a while. Rinse carefully with very hot water, scrub, then rinse again.
Be careful handling hot or boiling water, and wear closed-toe shoes.
Safety notes
- Protect your skin and eyes. TSP and strong degreasers are caustic. Wear gloves and safety glasses, and wash your hands after.
- Protect surroundings. Keep cleaners off lawns, plants, painted surfaces, aluminum, glass and car finishes. Wet nearby plants with plain water first to dilute any splashes.
- Ventilate. Open garage doors fully when working indoors.
- Mind your runoff. Don’t wash TSP or oily water into storm drains. Use absorbent to soak up residue and dispose of it in the trash, or follow your local household hazardous waste guidance.
- Never mix cleaners, especially anything containing bleach or ammonia.
Keep it from happening again
- Get leaking cars repaired. A slow drip will keep restaining your work.
- Put a drip pan or garage floor mat where you park.
- Apply a penetrating concrete sealer once the stain is gone and the surface is completely dry. It makes future spills much easier to clean.
- Consider a garage floor coating for a surface that wipes clean.
Seasonal tips for Philadelphia and South Jersey
Cleaners work best on dry days above about 50°F, so late spring through early fall is the time to tackle stains. In winter, oil and road salt tracked into garages create a slippery, corrosive mess. Clean up salty slush promptly, and plan any sealing for the fall so the concrete goes into freeze-thaw season protected.
When to call a pro
Stains are cosmetic, but some concrete problems aren’t. Call a pro if:
- The concrete is cracked, crumbling or flaking
- Your garage floor needs repair or a fresh start before coating
- Stains are on decorative, stamped or sealed concrete and you’re worried about damage
- You’d like your garage cleaned up, organized and made more usable
We take on garage projects, concrete and masonry repair, and exterior work for homeowners in Philadelphia, the suburbs and South Jersey. For fresh spills, check out Driveways and Sidewalks. When you’re ready, request a quote.
