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P0302 is a misfire in the number 2 cylinder.
If you are using excessive amounts of oil yet there are no leaks then it has to be burning the oil. If the oil consumption started at about the same time as the misfire code then I would start at the number 2 cylinder.
Start by removing the number 2 plug and see if there are signs of oil burning. If you don't see anything then I would move on to checking the others.
Excessive oil consumption could be caused by a stuck PCV valve, but is more likely to be a piston, ring, cylinder wall, or valve guide/seal issue. The misfire code may be because of low compression or because that cylinder is burning the large amount of oil.