Shares of Garmin (GRMN) - Get Report are down more than 4% Wednesday after analysts at Goldman Sachs downgraded the stock to sell from hold. The stock is down more than 6% since Friday. The stock was downgraded by Raymond James on Monday. 

Garmin makes great products and its fitness and outdoor segment has been strong, TheStreet's Jim Cramer, co-manager of the Action Alerts PLUS portfolio, said on CNBC's "Stop Trading" segment. 

However, investors have been expecting this stock to "roll over" for quite some time. Even with the recent decline, shares are still up almost 40% on the year, Cramer said. Goldman's "very well-reasoned piece" may be just what it takes to cause more selling.

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After talking about a couple of successful oil companies earlier, Cramer turned his attention to Valero Energy (VLO) - Get Report and Phillips 66 (PSX) - Get Report . These refineries will be the ones to feel the pinch should a gasoline glut pressure margins. 

Such a glut won't hurt the exploration and production companies or the large, integrated oil giants. But refiners will get hurt and investors need to be aware of that, Cramer warned. However, he didn't suggest shorting these names, partly due to their attractive dividend yields. 

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At the time of publication, Cramer's Action Alerts PLUS had no position in companies mentioned.