Carvana Co. (NYSE:CVNA) shares slipped in premarket trading on Thursday as investors weighed fresh earnings details and cost pressures.The online used-vehicle retailer delivered stronger revenue than expected, yet mounting operational expenses and short-seller scrutiny shaped early sentiment around the stock.Quarterly PerformanceCarvana posted fourth-quarter revenue of nearly $5.6 billion, surpassing analyst projections that tracked closer to $5.26 billion. The company also disclosed earnings of $4.22 per s ...