With Krastorio 2, the oil mining recipe defaults to whichever miner you have set as default, instead of pumpjacks. This makes the projected output incorrect. Clicking on the recipe to change the miner allows you to change it to pumpjacks, at which point it stays fixed and won't let you switch back to miners.

However, each new oil production line you create has this issue. Confused me quite a bit until I noticed, since I could never get the math on oil production to line up like it should have.

I suspect this is because K2 changes oil to be a finite resource.