Leaded vs Unleaded Petrol: Health, Engine & Environmental Impact
Leaded petrol contains tetraethyllead to boost octane and cut engine knock; unleaded petrol is the same fuel minus this toxic metal compound.
At the pump the labels look almost identical, so drivers who grew up before the 1990s still say “fill it with leaded” out of habit, even though every modern bowser dispenses unleaded.
Key Differences
Leaded petrol lowers IQ in children, fouls catalytic converters and soils urban dust for decades. Unleaded keeps engines, lungs and rivers cleaner, but needs extra refining additives to reach the same octane.
Which One Should You Choose?
You can’t choose—leaded petrol is banned for road use in almost every country. When you see “premium” or “regular,” you’re already buying unleaded; just match the octane number in your owner’s manual.
Examples and Daily Life
Classic car rallies in Europe use a small-lead substitute additive, while lawn-mower fuel bought at a rural station in Kenya might still be leaded. Your modern hatchback’s unleaded fill-up powers the same trip without the health bill.
Does unleaded petrol harm my engine?
No—modern engines are engineered for it; using leaded would wreck the catalytic converter and oxygen sensors.
Is aviation fuel the same as leaded petrol?
Not quite. Avgas 100LL still contains lead for high-altitude performance, but it’s illegal in cars.