Deutsche Bank downgraded Westport Innovations (NASDAQ: WPRT) from Buy to Hold with a price target of $8.00 (from $12.00). Analyst Vishal Shah thinks weak oil prices could impact the company's performance.

"Weak oil price environment could continue to impact near term adoption of NG vehicles and uncertainty about timing of cash flow break-even could remain near-term headwinds for the stock. While we believe mgmt has kitchen-sinked guidance/expectations and is likely to rein in expenses/investments in order to reduce cash burn in the near term, we see limited near term catalysts," said Shah.

"The company remains on track to achieve positive EBITDA break-even targets for 2015 and progress on warranty expenses remains encouraging. But until there is more evidence of EBITDA improvement or OEM/product announcements, we expect shares to remain range-bound," he added.

For an analyst ratings summary and ratings history on Westport Innovations click here. For more ratings news on Westport Innovations click here.

Shares of Westport Innovations closed at $6.05 yesterday.