Volvo is warning its customers of the possibility of sudden acceleration in eight different models using the five-cylinder diesel engine.  Vehicles involved in the warning include the 2006-2010 S40 and V50, 2007-2009 S80, 2007-2010 C30 and C70, 2008-2009 V70 and XC70, and the 2009 XC60.

A recall has not yet been issued for those vehicles.  Volvo will be sending a letter warning owners of the 158,000 units sold across Europe.

In an interview with CNN, Volvo Cars spokesman Per-Ake Froberg said that the issue is engine oil leaking into the combustion chamber.  This works in the same way as fuel and causes an acceration burst.

"This has caused the engine to maintain or even increase its speed, even though the driver has removed his foot from the gas pedal," he said.

Froberg says that biodiesel mixed with conventional diesel is the primary cause, as it does not evaporate in the same manner as normal diesel fuel.  This leads to extra fuel injected through the particle filter, which does not combust, and instead winds up combined with the engine oil.  The oil level subsequently rises, and overflows into the combustion chamber.

Thus far, Volvo claims 55 incidents of sudden acceleration have been reported to the automaker.

"We have not had any accidents reported as a result of this, though. In the instances when this has occurred, the drivers have put the gear in neutral and stopped on the side of the road," Froberg said.

Volvo does not yet have a solution to the problem.

Gallery: Volvo issues unintended acceleration warning for some models

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