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: Penske Automotive Group (NYSE: PAG) shares broke the 10% threshold shortly after noon ET today, fueled by a solid earnings report.

So what: The automotive retailer announced a 50% increase in per-share profits this morning, easily beating analyst estimates. CEO Roger Penske himself admitted that the company's $0.39 profit from continuing operations "exceeded my expectations." That's especially impressive when you consider that total revenue rose only 15%.

Now what: True, Penske cautioned that the crisis in Japan could crimp supplies of Toyota (NYSE: TM) and Honda (NYSE: HMC) vehicles later this year. (Toyota and Honda together make up about one-third of the vehicles Penske sells annually.) Regardless, the shares appear to price in that risk already. Based on current results, Penske costs barely 17 times trailing earnings, yet analysts expect it to grow these earnings at better than 18% annually over the next five years. No wonder the shorts are fleeing -- and the shares are spiking.

Is Rich right? Does Penske still have gas in the tank? Add it to your Watchlist and find out.

Fool contributor Rich Smith does not own shares of Penske, but the Fool does. The Motley Fool has a disclosure policy. Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.