For a fresh spill, do not start by hosing it down. Absorb free oil with a suitable absorbent so it does not spread or soak deeper into the slab.
Collect the absorbent carefully
Dispose of oil-contaminated material according to local requirements, especially when the spill is motor oil or another automotive fluid.
Use a concrete-compatible degreaser
Wet the surface only if the product directions call for it, scrub with a firm nonmetallic brush, and allow the labeled dwell time.
Control the rinse water
Do not push oily runoff into storm drains. Capture residue when required and follow local wastewater rules.
Old stains may need repetition
Oil can penetrate pores and leave a shadow after most residue is gone. Several moderate treatments are often safer than jumping to acid or highly aggressive chemicals.
Test decorative concrete first
Sealed, colored, or coated concrete may react differently from bare gray concrete.
Confirm what actually leaked before choosing a cleaner
A dark automotive spot may be engine oil, but coolant, brake fluid, transmission fluid, and other products have different cleanup and disposal concerns. If the spill is still active, fix or contain the vehicle leak first; repeatedly cleaning the slab will not solve the source.
For fuel, solvent, or a large spill, safe containment and disposal matter more than cosmetic stain removal.
Sources
- American Cleaning Institute — Cleaning Tips — Household cleaning, product-label use, and stain-treatment principles.