Leaky Oil Fissure
Leaky Oil Fissure is a renewable source of Crude Oil, which can be found in Caustic Biomes. It is not guaranteed to spawn.
It should not be confused with Oil Reservoirs, which are guaranteed to spawn naturally in the Oil Biome, and need an Oil Well to produce oil. In contrast, Leaky Oil Fissure produces Crude Oil on its own and doesn't need Water or Power to do so.
Taming
The oil produced by a Leaky Oil Fissure is too hot to be handled by Steel machinery, so some cooling is necessary if handling it using pre-space age materials. A single self-cooling Steam Turbine is sufficient to cool up to 875 g/s of oil, much more than the typical fissure produces, to 130 °C, well within the safe operating range for self-cooling.
With access to space-age materials, it may be preferable to simply build a Thermium Thermo Aquatuner directly adjacent to the fissure and boil the oil directly to Sour Gas, bypassing liquid infrastructure altogether.
Its good to note that Leaky Oil Fissures will never go Idle but they do have a "dormant" period which acts more like an idle period as it stops erupting for a very short amount of time; this dormancy period lasts 40 s - 400 s, averaging 220 seconds (less than half of one cycle).
Tips
Crude Oil emitted by the fissure is a very good feedstock for a Petroleum Boiler, as it only needs to be heated by about 76°C to turn into Petroleum. In contrast, Crude Oil produced by an Oil Well is "only" 90°C or hotter, meaning it has to be heated by about 313°C to turn into Petroleum in the worst case.
However, be warned that mixing feedstock to the common counterflow boiler design may result in pipes bursting or pump damage due to its high temperature - not only is it hot enough to damage Steel machinery itself, it will not provide adequate cooling for the output Petroleum if it is built to expect lower-temperature Crude Oil (such as from an Oil Well).