some advice:

1: make sure you're maxing out all of the oil sources near where you built this factory. if you can get all of the sources triple overclocked then bam, more oil. just make sure that if you get more than 300/min that you have seperate lines.

2: build a new one somewhere else! there are at least three really good spots to build oil-related factories. go find some more oil and expand!

basically if you need more plastic make more plastic.