For reference: Nissan e-power with recuperation ~50%: https://www.nissan-global.com/EN/INNOVATION/TECHNOLOGY/ARCHI...
Mahle ~45% with pre-chamber: https://www.mobilityengineeringtech.com/component/content/ar...
Toyota dynamic force engines ~40% : https://www.thedrive.com/tech/18919/toyota-develops-worlds-m...
Toyota's newest engines claim even more: https://global.toyota/en/newsroom/corporate/40850156.html
Honda hybrid ~40%: https://hondanews.com/en-US/honda-automobiles/releases/relea...
Startup Carnot engines claim 70% efficiency: https://carnotengines.com/technology/