Any cooking oil will burn in a wick lamp, and olive oil burns with the least smoke and smell. Sunflower and rapeseed oil are good, and used cooking oil still works as fuel even when it is too rancid to eat. Because plant oils are liquid at room temperature they spill more easily than fat, so use a lamp with a lid or a narrow neck.
Part of Oil Lamp Construction
Plant oils are liquid at room temperature, so they climb a wick readily but also spill readily, which favours lidded or narrow-necked lamps.
Plant Oils Wick Easily But Spill Easily
The oil-lamp overview lists these oils:
- Olive oil — burns the cleanest, almost no smoke or smell. Used in Mediterranean lamps for millennia.
- Sunflower and rapeseed oil — good and widely available.
- Nut oils (walnut, hazelnut) — excellent fuel but precious; the overview says they are better eaten.
- Used cooking oil — works for lighting even when too rancid for food.
A liquid oil climbs a wick more readily than molten fat, which is why oil lamps are easy to start. The cost is spilling: a tipped open dish spreads a sheet of burning oil across a table. A lid, a narrow-necked reservoir or a closed-reservoir lamp limits that. If you press your own oil, Oil Extraction covers the method.
Used Oil Must Be Cleaned First
Used frying oil carries food particles and water. Both foul a wick.
- Let the oil stand in a tall container for a day so that water and sediment sink.
- Pour or ladle the clear oil off the top without stirring up the bottom.
- Strain through cloth.
If the lamp spits or crackles, water is still in the oil: settle and decant again.
Worked Example
The overview gives about 30 ml/h at a moderate wick for vegetable and olive oil.
- One litre lasts 1,000 ml ÷ 30 ml/h ≈ 33 hours.
- A four-hour evening uses 4 × 30 = 120 ml.
- One litre therefore covers 33 h ÷ 4 h ≈ 8 evenings.
Common Mistakes
- Burning edible oil when food is short. The overview calls nut oils better eaten; the same reasoning applies to any oil you need as food.
- Filling an open dish to the brim. A full dish spills at the first knock. Fill only to where the wick end is submerged.
- Skipping the settle-and-decant step on used oil. Water and food particles are the usual cause of a sputtering lamp.
Safety
Oily rags and spilled oil
A rag, wick offcut or cloth soaked in plant oil can heat itself as the oil oxidises, and a pile of such rags can ignite without any flame near it. This is a particular risk with oils that dry, such as linseed. Spread oily rags out to dry outdoors on a non-combustible surface or burn them in a controlled fire; do not leave them bunched in a corner or a bin. Spilled oil burns like any fuel: smother with a lid or dry sand or earth, never water. Even clean-burning olive oil makes soot if the wick is too high, and soot means incomplete burning and carbon monoxide; ventilate with an inlet and an outlet.
What’s Next
- Learn next: Closed Reservoir Lamp — a design that suits a spill-prone liquid
- Combine with: Cotton & Plant Fiber Wicks — a wick that lifts oil well