Wärtsilä 31, which claims to be the most efficient engine ever built, claims 167.7g/kWh. Diesel's engine used 317g/kWh. So the amount of fuel used has not eve

Wärtsilä 31, which claims to be the most efficient engine ever built, claims 167.7g/kWh. Diesel's engine used 317g/kWh. So the amount of fuel used has not even halved in more than a century.