Tesoro (TSO) -7.5% premarket after issuing downside guidance due to an "extremely weak margin environment in California and the collapse of the West Texas Intermediate to Brent crude oil spread." The refiner sees a Q4 EPS loss of $0.55-$0.80 vs. consensus $0.67 loss, and FY12 EPS of $3.85-$4.10 vs. consensus $5.34.