Why does a drop from $100-87/barrel in oil prices result in a 10 cent drop in gas prices BUT if it raises from 87-100 the increase is 30 cents?

What are gas prices around diferent NE states? Conectcut today 3.12/gal regular about 35 cent more for 93 oct.

 

Regular is $2.97 up to $3.05 depending on where in Southeast Mass you go.
Of course the tax structure is different in each state.