But I've done a bit of checking, and my thoughts are that first off, California has a VERY tight balance between refining capacity and population--with about 10% of national poulation, and 10% refining capacity--and is pretty much completely average in use of transportation fuels.
You may have to open the tabs to see the numbers--but look at the "Overview" "Reserves and Production" and "Consumption" tabs specifically to see the numbers.
http://www.eia.doe.gov/state/state-energy-profiles-data.cfm?sid=CAThis means that it can supply itself adequately--as long as everything is working and running. Right now it looks as though one or more of CA's refineries is doing maintenance and the state is drawing down its stocks of finished gasoline. Most refineries do their maintenance cycles in the Winter so that they can go balls out to meet our summer demand spikes.
Coupled with CA's own unique and stringent formulation requirements (not many places can make gasoline to sell in California--even if there were a way to get it there you wind up living with a tight balance of supply.
Please notice how CA's current stock of gasoline is less than half what WA has--or even MN for that matter. It is also half what it was this summer. (Gramted--these numbers are from November, so I'd suspect that we are either at the bottom of the trough right now, or quite possibly on the way back to building inventories.
http://www.eia.gov/dnav/pet/pet_stoc_st_a_EPM0F_STR_mbbl_m.htm