General Motors Co. (GM) is once again the most valuable U.S. car company, overtaking Tesla Inc. (TSLA) which has experienced a sharp downturn this week following weak production estimates and an unfavorable crash test rating from the Institute for Highway Safety. 

Tesla shares were down nearly 6% Thursday afternoon, lowering the company's value to $50.6 billion while GM is valued above $52 billion. 

Tesla's week had a rough start after CEO Elon Musk tweeted that the electric car maker anticipates producing 20,000 vehicles a month beginning in December, below market guidance. News that Volvo (VLVLY) would begin producing only electric and hybrid vehicles by 2019 also put pressure on the stock price. 

GM shares fell 0.4% to $34.88 by Thursday's close.

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Apple is OK for the time being: For those silently worrying how the Apple (AAPL) iPhone 8 will sell, simmer down -- the tech giant still has several huge advantages. On the hardware side, for instance, the iPhone still feels ahead of the pack thanks not only to Apple's design skills and the visible features of its hardware, but also what's under the hood points out TheStreet's tech columnist Eric Jhonsa. From the looks of things, the iPhone 8 should extend that lead, Jhonsa predicts.

Tesla is looking wobbly: Tesla (TSLA) shares are looking a little shaky (again) after its Model S didn't get a top rating from Insurance Institute for Highway Safety (IIHS), reports TheStreet's James Skinner. The IIHS cited issues with the small overlap front test, which is meant to simulate crashes into trees, poles and other vehicles, as why the Model S did not receive the highest rating. IIHS Executive Vice President David Zuby said the front test remains a "hurdle" for some vehicles.

"Tesla made changes to the safety belt in vehicles built after January with the intent of reducing the dummy's forward movement," IIHS said. "However, when IIHS tested the modified Model S, the same problem occurred, and the rating didn't change."

Costco finally scores some good news: After watching its stock crash about 13% inside a month thanks to fears Amazon (AMZN) and Whole Foods (WFM) will dominate society, Costco COST scored a nice win. Costco said same-store sales in June rose 6.5% in June. Canada saw sales up 3.2%, while international sales rose 6.2%.

The numbers should serve as a reminder how resilient Costco's business has been in the face of Amazon's rise.

Apple is a holding in Jim Cramer's Action Alerts PLUS Charitable Trust Portfolio. Want to be alerted before Cramer buys or sells AAPL? Learn more now .

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