Other mistake: When "the killer" is pumping gas, if you count the clicks associated with a liter going into the tank, they equal a total of 33 liters of gas, not 27 which is what the pump stops on.
Continuity mistake: When Marie is in the back of the van taking the chains of Alex, Alex picks up the knife and it is obviously bent. Once the chains are off and Alex puts the knife up to Marie to defend herself the blade is straight, and stays that way even when "the killer" takes it out of his chest.
Answer: It is impossible to know which vehicles were actually used, or even what really happened throughout the movie. The plot twist at the end of this film, while certainly surprising, was not very thoroughly planned out. It's almost as if the writer decided at the last minute to add it for no better reason than he couldn't think of a way to end the movie.
Phixius