Polutions caused by oil are greatly exaggerated and would not harm a fly, nor there is side effects in humans*. If you see a dead fly, your monitor most like has broken pixel.
Here is example picture of 4MW power plant. The place use to be just refinery, but was later relocated and two 0.1/s crude oil sources were left behind. The power plant powers itself and rest of the capasity is used to power main grid via accumulators.
![Image](https://forums.factorio.com/images/ext/0ef38213770760442b875eb0214eb1dc.png)
Below is my exel chart chart of 6 variations of above plant. Production cost in chart is average. Its bit peaky in game, but efficiency modules does tone it down. Boiler losses are not shown in production cost. (Excel sheets here)
![Image](https://forums.factorio.com/images/ext/51a765c0abe40d5cc8843364d2daa3bb.png)
y-axel values are in kW
+cracking means heavy to light cracking, instead of turning heavy directly to solid fuel.
+2xspeed 3 means two "speed modules 3" in both Pumpjacks.
+efficiency means oil refinery and all chemical plans have -80% consumption.
*As long as you wear protective equipment