Tesoro Shares Plunged: What You Need to Know in 2012

Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.
What: Shares of Tesoro (NYSE: TSO  ) are plunging today, down by as much as 10%, after the company updated its fourth-quarter guidance.
So what: The company expects to report a net loss between $0.55 and $0.80 per share, compared to the $0.65 profit analysts are looking for. Tesoro cited an extremely weak margin environment in California and the collapse of the West Texas Intermediate (WTI) to Brent crude oil spread.
Now what: The Tesoro Index for the California area was a negative $0.05 per barrel, down over $6 compared to the sequential and year-over-year prices. The WTI to Brent spread fell from $26 per barrel in September to just $8 per barrel in December. The decline reduces benchmark margins at Tesoro's refineries and the margin on long-haul foreign crude oil barrels indexed to WTI. When you're in the oil business, volatility is simply the name of the game.