Burning oil? I have had a similar idea for a long while.
The idea is that You need to construct lamp posts underground to keep field of vision over that area. without them dwarves have to walk in the dark with very limited vision range. Naturally they refuse to work anywhere they cannot see, except to haul things around in which case they have to reroute everytime they realize an obstacle.... generally not something you want to do.
Oil is made from fat. The more skilled the operator the more oil produced from a single unit of fat. It has no quality modifier.
Lamp post can be constructed with a stone/wood, a bucket and a rope, lamp posts require oil to operate and will consume them over time. Lamps can be tasked to turn on/off. Lamp post can hold a limited amount of oil. Better constructed lamp posts consume less oil and/or provide more vision.
Oil tanks are 3x3 buildings built from 3 blocks, a barrel and a pipe. It can hold as much oil as about 25 lamp posts and act as lamp posts themselves. They can be linked to other oil tank using pipes and other lamp posts in the same z level using mechanisms. Once linked, tanks share fuel and automatically fuel any lamps they are linked to. However, there must be an existing path provided by lamp post/tank vision between the oil tank and the destination lamp post for them to be linked. The lamp posts in between can be turned off after linking, though. Links between oil tanks while can be done regardless of distance if you have enough pipes, consume extra oil (they leaks away) Pipes do not hinder creature movement but buildings cant be built over them.
Both lamp posts and oil tanks explode when exposed to fire and has a large chance of doing so when destroyed. This will greatly burn and spill !!Oil!! to surrounding area. Needless to say oil tanks are more likely to do this, and to greater effect then simple lamp posts.