What is the reason for Toyota Highlander's high fuel consumption?

There may be two factors. The first factor is the vehicle itself. Cleaning carbon deposits and fuel injectors is one aspect. In addition, whether the tire pressure is normal, whether the wheel bearing or braking system is delayed, and whether there are related faults in the engine electronic control system will all affect the increase of fuel consumption. For the vehicle itself, I suggest you go to the 4S shop for a detailed inspection. The second is external factors. For example, if you often drive on congested roads with the same fuel consumption, the mileage will be reduced accordingly. Therefore, for the problem of increasing fuel consumption, you should combine your own environmental analysis to see if there is any difference. If the fuel consumption suddenly rises in the same environment, it is recommended to go to the 4S shop for a detailed inspection of the vehicle.