I noticed when prices first went nuts, that - much like I remember from way back when gas was $1/gallon - it was still about a $0.10 jump from both regular -> plus and from plus -> premium. Then, it started to creep a little, I'd say maybe six months ago or so, but it wasn't linear. Regular -> plus was $0.15 but plus -> premium was still $0.10. Now, it's even more bizarre. This morning I noticed one station with a THIRTY-ONE-cent difference regular -> plus but still only like $0.12 from plus -> premium!
Evidence of some actual change in the refining process, or just another example of gas prices being sent by a blindfolded monkey and a dartboard?