function Car(color) {
  this.color = color
  this.automatic = false;
  this.satnav = false;
  this.radio = true;
  this.mot = null;
}

Car.prototype = {
  addFuel: () => {
    console.log('just added fuel to your car')
  },

  washCar: () => {
    console.log('your car just got washed')
  }
}

const BMW = new Car('red');
BMW.addFuel(); // Just added fuel to your car
console.log(BMW.color) // red
console.log(BMW.satnav) // false
BMW.satnav = true;
console.log(BMW.satnav) // true