We definitely need to know if your oil industry is from the Industries DLC or if it's the old zoned industry specialisation. There's a few different resources which come out of these, and knowing which one the plant uses is important.
Extractors all produce crude oil (just called oil in game). It's the same resource no matter if it's the DLC extractors or the zoned extractors. This is NOT what the plant uses though (I thought it was for years until I discovered that wasn't the case).
Zoned oil specialisation also has processor buildings. These take the crude oil and refine it into what the game called "Zoned Industry - Oil Products" (that's the option on warehouses if you have Industries). This is what the oil power plant uses, and is also used by generic industry.
The DLC areas refine crude oil into either plastics or petroleum. This is only used by unique factories or exported. The power plant can't use this.
And lastly there's the large refi...
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