What you're actually dealing with
Fresh oil (under 7 days) sits on the surface and lifts easily.
Recent oil (1–6 months) has soaked into the top millimetre of block, slab or concrete. Still very removable.
Old oil (6+ months) is bonded with the surface. Lightening is realistic; full removal often isn't.
Diesel and hydraulic fluid behave differently to engine oil — they evaporate the volatile element and leave a sticky residue that traps dirt. Same removal method, but the result tends to look better afterwards.
Methods that don't work
Washing-up liquid and a hose — moves the oil around, doesn't lift it. Often spreads the stain.
Sand or cat litter alone — absorbs surface oil but leaves the soaked-in portion untouched. Fine for a fresh spill, useless for an established stain.
Domestic pressure washer with plain water — drives the oil deeper into porous surfaces and lifts the surface skin off concrete blocks.
Bleach — does nothing to oil. Pure marketing for products that include it.
The method that works
Step 1: Absorb. Sprinkle cat litter or sand on a fresh spill, leave overnight, sweep up. Skip this for old stains.
Step 2: Degrease. Apply an alkaline (high-pH) degreaser specifically formulated for masonry. Brush in. Leave to dwell 10–20 minutes — this is what does the work.
Step 3: Hot pressure wash. The degreaser plus heat plus pressure lifts the oil from the pores. A rotary surface cleaner works far better than a wand for evenness.
Step 4: Repeat once if needed. Most stains lighten dramatically on the first pass and disappear on the second.
Step 5: Re-sand block paving joints with kiln-dried sand. Any cleaning method strips some joint sand — replacing it stops weeds and keeps the blocks stable.
When the stain is permanent
Engine oil that's been sitting for 2+ years on concrete or unsealed slabs has usually penetrated below the top layer. Cleaning can lighten it 50–70% but a faint ghost remains.
Tarmac stains can be lifted but the binder in tarmac is itself bitumen — aggressive degreaser can soften the tarmac surface. Specialist tarmac cleaner only.
If full removal matters (selling the house, etc.) and the stain won't lift, block replacement is usually £30–£80 for the affected blocks and 30 minutes of work.