Why hosing does nothing
Concrete is porous — a network of tiny capillaries running down from the surface. Motor oil wicks into that network and stays there. Water applied to the surface never reaches it, which is why a pressure washer alone lightens the edges of an oil stain and leaves the middle untouched.
What actually works
A degreaser with enough dwell time to penetrate and emulsify the oil, so it can be lifted back up out of the pores. Then hot water extraction to carry it away. Skip the dwell time and you have moved oil around. Skip the heat and you leave a film that re-darkens within a week as it oxidises.
Household methods and their limits
Cat litter absorbs fresh oil before it soaks in, and it is genuinely worth keeping some in the garage for that reason. Dish soap emulsifies a light surface film. Neither reaches oil that has been sitting for months. Concrete poultice products can work on small deep stains but need repeated applications over days.
What never to do
Do not use a wire brush — it polishes and scores the surface, which makes the area hold dirt faster afterward. Do not use muriatic acid on a stain; it etches the concrete and leaves a permanently lighter patch that is more noticeable than the oil was. Do not hold a narrow-angle tip close to the surface, which cuts visible lines into concrete.
When it is genuinely permanent
Oil that has been in place for many years, especially on older porous concrete, may lighten dramatically rather than disappear. A good company tells you that before starting rather than after. In those cases the honest options are accepting a much-improved result, or resurfacing.
Key points
Why hosing does nothing
Concrete is porous — a network of tiny capillaries running down from the surface. Motor oil wicks into that network and stays there. Water applied to the surface never reaches it, which is why a pressure washer alone lightens the edges of an oil stain and leaves the middle untouched.
When it is genuinely permanent
Oil that has been in place for many years, especially on older porous concrete, may lighten dramatically rather than disappear. A good company tells you that before starting rather than after. In those cases the honest options are accepting a much-improved result, or resurfacing.