If you're slowing down to traffic light, it's more efficient than coasting in neutral. You've to slow down anyway and slowing down with engine braking is 0.0l/k

If you're slowing down to traffic light, it's more efficient than coasting in neutral. You've to slow down anyway and slowing down with engine braking is 0.0l/km. While coasting still burns some fuel. In addition to that, some newer cars charge battery when engine braking. Which is effectively saving fuel later.