The unsub who runs his victims down with his car changes his bumper and license plate each time. He is shown doing this always with Oregon plates. Later, when Rossi and Morgan find his discarded sets, they are California plates.
When the unsub is chasing down his victim in the parking garage, the trucks headlights are on, but in a number of shots, they're turned off.
While inspecting the car (a late model BMW) in the impound lot, the agents surmise the heater hose was cut without opening the hood. On late model cars, the radiator is sealed to the core support so no air (or other objects) can get around the radiator. It would not be possible to cut the heater hose without opening the hood. This particular model is also equipped with a low coolant light that would have illuminated once the driver started the motor.
Additionally, there are many variables involved with a car overheating, such as using the air conditioning, outside temperature, humidity, etc. There would be no way to exactly determine where it would stop due to overheating.
License plates in Oregon are three letters followed by three numbers (ABC123). They are never a mix of numbers and letters, like the license plate on the unsub's truck, unless it is a specialty plate.
The killer was targeting people on route 7; however, Oregon Route 7 is located in eastern Oregon, between Austin and Baker City. There is no direct highway route between Bend and Eugene. They got the other roads right - routes 20 and 26 - where the chase for the truck occurred.
The scene at the police station just after the third murder briefly shows a map of Bend, OR, where the three victims drove regularly. This is where they deduce that Route 7 is the common factor in the crimes. The map is obviously doctored: three of the roads (27th St, Bear Creek Rd, and Ward Rd) are correct. But the infamous Route 7 is obvious relabeled from the real US 20. It even still uses the US highway system shield. But US Rt 7 is a north/south highway in New England, not anywhere near Oregon.