Engine oil
Not simply an oil. Used engine oil carries combustion soot and metal particles, which is why it marks darker and behaves worse than the oil that went in.
In detail
Fresh engine oil is a refined mineral or synthetic base with additives; used engine oil is that plus everything the engine put into it — carbon from incomplete combustion, fine metal particles from wear, fuel dilution and oxidation products. The difference matters for cleaning because it is no longer a single-phase problem. The oil fraction responds to a solvent or a lipase-containing detergent; the carbon fraction is a fine particulate that behaves like soot, penetrating fibre and surface texture and smearing rather than lifting when wetted. That is why used oil leaves a grey shadow after the greasy feel has gone. On fabric it belongs to the solvent branch, with the oily fraction dealt with before any water. On porous outdoor surfaces the paving guidance applies unmodified: oil penetrates readily, so a spill is lifted promptly with an absorbent — paper towel, cat litter, cornflour or talc — and must NOT be wiped, because wiping drives it in and spreads it. And on skin the temptation to reach for the solvent that cleaned the part is the wrong move. Used oil is disposed of as hazardous waste rather than down a drain.
What works
Hand cleanser is effective against Engine oil Established practitioner practice
The evidence here is about why a solvent is the wrong choice on skin, not about how well any particular cleanser works.
Why
- Engine oil is explained by Why oil resists water
- Engine oil is explained by Penetration into fibres
- Engine oil is explained by Why old stains are harder
Sources for this page
Sources
Cleaning & Maintenance Guidelines — Gardens & Driveways
Marshalls plc · Manufacturer documentation
Relied on for: That oil penetrates paving readily, that spillages are lifted promptly with an absorbent such as paper towel, cat litter, cornflour or talc, and that the stain must not be wiped because wiping drives it in and spreads it. (states this directly)
Spot Solver: spot and spill removal procedures
The Carpet and Rug Institute (CRI) · Trade or professional body
Relied on for: That vehicle oil and old oxidised oil are routed to the solvent branch, opening with nail polish remover or a dry-cleaning type solvent before any water. (states this directly)
Household Hazardous Waste (HHW)
United States Environmental Protection Agency (EPA) · Government or regulator
Relied on for: That certain household products must not be poured on the ground or into storm sewers and require hazardous-waste disposal routes. (states this directly)