Warrnambool police Sergeant Greg Cressall said the P-plater was travelling east about 1am on the Warrnambool-Cobden Road near Naringal when he noticed smoke and flames emerging from the engine bay.

"He immediately pulled over, the vehicle became fully engulfed in flames and was completely destroyed. The driver was not injured," he said.

Sergeant Cressall said the incident happened between Craigs Lane and Bartons Road.

"It's very unusual, there are no suspicious circumstances and I'm sure the driver would have been left shaken," he said.

"We assume it was an electrical or mechanical fault that caused the fire," he said.