That's why I talked about hybrids - ICEs have slim efficiency area, add breaking lossess and you get to that number. But put it in a hybrid and you can run it at near-max efficiency most of the time and don't waste that much in breaking.
Hell, Formula engines get to 50% but those don't exactly need to care about emission equipment
Hell, Formula engines get to 50% but those don't exactly need to care about emission equipment