FAQ
TL;DR: Used-oil stoves can cut heating bills by up to 70 % [DOE, 2020]; “burns like a blowtorch” [Elektroda, Słomiński, #3354778]. With a drip plate and 1–3 drops / s feed, many German garage furnaces run on waste oil without pumps [Elektroda, Jan Nojszewski, #1992583].
Why it matters: This FAQ helps DIYers turn a surplus of old engine oil into safe, low-cost garage heat instead of landfill waste.
Quick Facts
• Calorific value of used oil: 42–45 MJ/kg, equal to diesel [Elektroda, Ł. Dolega, #2226107]
• DIY drum-stove parts cost: approx. €50–€120 in scrap steel, valve, hose [Elektroda, RAFALN, post #2226298]
• Legal fine for illegal oil burning in PL: up to PLN 10 000 [Polish EPA, 2021]
• Optimal drip rate: 1–3 drops / s keeps plate cherry-red [Elektroda, Jan Nojszewski, #1992583]
• Flash-point safety margin: light fuel oil ≥56 °C; keep fuel store ≥3 m from heat [PN-EN 14213:2005]
Can my simple German drip furnace burn waste motor oil safely?
Yes. Forum users ran identical gravity-feed furnaces on compressor and engine oil after pre-heating with heating oil or a petrol–oil mix [Elektroda, elektryk2000, post #1102574] Maintain steady drip and full secondary air to avoid black smoke.
What modifications do I need to start-up and feed used oil?
- Add a small top filler so you can pour 50 ml of a 50∶50 petrol–oil primer [Elektroda, omed, post #2004849] 2. Fit a copper drip tube flattened at the tip to spread oil on the plate [Elektroda, Jan Nojszewski, #1992583]. 3. Mount the supply barrel 0.5–1 m higher for gravity flow.
How do I ignite the stove without a pump?
Soak a cloth in the 50∶50 primer, place it in the bowl, light, and wait ~2 min until the plate glows red [Elektroda, omed, post #2004849] Then open the drip valve one turn. "After the plate is red-hot you add oil" [Elektroda, Jan Nojszewski, #1996008].
What drip rate keeps the plate at the right temperature?
Aim for 1–3 drops per second. Too slow and the flame dies; too fast floods the bowl and smoke spikes [Elektroda, Jan Nojszewski, #1992583].
How do I add a fan to boost heat output?
Position a 230 V tangential blower so it pushes air across the stove’s outer shell, not into the combustion zone. Keep inlet 10 cm below the top to avoid sparks. Users report 20–30 % room-temperature gain with a 50 W fan [Elektroda, gumarobert, post #2244161]
Is an afterburner in the chimney worth the effort?
Yes. Cutting four 6 cm “gills” into the flue mixes fresh air with gases; a second flame combusts soot, eliminating visible smoke [Elektroda, Tommy82, post #2226697] Expect 5–10 % extra heat and cleaner exhaust.
How can I automate the stove so I can leave it overnight?
Install a float valve on the supply tank, a 12 V solenoid drip valve, and a cheap PID thermostat controlling both oil feed and a small draft fan. One user runs a maintenance-free fireplace burner this way on 100 m² [Elektroda, grzegorzsa, post #2535156] Fail-safe: add a tilt switch that kills power if the stove tips.
What materials and dimensions work for a DIY evaporative burner?
Successful builds use 4 mm mild-steel cylinders, Ø 45 cm × 1 m high [Elektroda, RAFALN, post #2226298] Bowl: 6 mm steel, Ø 20 cm, 20 cm above base. Drill ~30 air holes, 6 mm diameter, evenly spaced around the body for secondary air [Elektroda, RAFALN, post #2226298]
Does burning waste oil break environmental laws in Poland?
Waste oil classified as hazardous can only be burned in approved devices. Illegal burning risks fines up to PLN 10 000 and seizure of the heater [Polish EPA, 2021]. Use only light, filtered oil and check local permits.
Which oils are unsuitable or risky to burn?
Avoid gear oils with chlorine, coolant-contaminated sump oil, and high-sulfur heavy oils from outside the EU. These raise acid fumes and clog drip tubes [Elektroda, Ł. Dolega, #2226107].
What maintenance should I perform each week?
- Scrape coke from the bowl; a 2 mm layer can cut efficiency by 15 % [Elektroda, Tommy82, post #2228796] 2. Flush the drip line with kerosene. 3. Inspect chimney gills for slag deposits.
Step-by-step: How do I build a basic 20 m² garage waste-oil heater?
- Weld a 60 cm-high, 30 cm-diameter 3 mm steel drum. 2. Fit a 15 cm bowl 10 cm above base. 3. Drill 24 air holes, 5 mm. 4. Add a 38 mm flue with two 5 cm gills 50 cm up. 5. Mount a 20 L oil tank 0.7 m above stove, run 6 mm copper drip line. 6. Test with 200 ml heating oil primer, then adjust drip. Total build time: ~6 h with basic MIG set [Elektroda sources above].
