Tesla shattered Wall Street's profit forecast for the third quarter. But these 6 analysts are questioning how long it can last.

Price target: Raised to $220, up from $200

Rating: Underweight

"While we have some questions about the sustainability of gross margin strength exhibited during the quarter, operating expense tracked lower and the DCF-based portion of our valuation analysis benefits from the lower trend to capital expenditures," JPMorgan analysts wrote

Price target: Bumped to $200, up from $189

Rating: Underperform

"The question moving forward is on the sustainability of the results," Credit Suisse analyst Dan Levy wrote in a note to clients on Thursday.

Levy added: "Our take – a strong step forward, yet Tesla will need to put together a string of similar datapoints to demonstrate the sustainability of results...and its track record has been spotty on this."

Price target: Increased to $220, from $190

Rating: Underperform

"Cost control can help a quarter, but we struggle to understand how spending doesn't have to go up to support Tesla's growth ambitions," RBC Capital Market's analysts said in a note to clients on Thursday.

They added: "Tesla already hinted that margins could start to take a step back in 4Q19 as China factory comes online."

Price target: Raised to $235, from $225

Rating: Underperform

"The one very concerning aspect of the quarter was that top-line growth reversed to a decline, with 3Q:19 deliveries up a mere 2% sequentially from 2Q:19, but, more importantly, revenue down 8% YoY, marking the first decline in seven years for the "growth" company," Bank of America analysts wrote in a note to clients on Thursday.

The analysts continued: "Moreover, further growth will naturally require incremental cost and cash use, putting profitability and cash flow targets at risk soon."