We have this claim from September 2017 https://www.autosport.com/f1/news/13177 ... yno-targetTommy Cookers wrote: ↑12 Jul 2018, 13:20Andy Cowell has never said eg that their PUs are 50% efficient .....
but many believe that he has said this and therefore that 50% bte is an actuality
"Mercedes' Formula 1 engine has hit a landmark achievement on the dyno at the team's Brixworth factory after breaking the 50% thermal efficiency barrier for the first time.
The 50% mark, which has not yet been reached on track, is much higher than a reported 29% efficiency peak that old normally-aspirated V8 engines produced.
Mercedes' first turbo-hybrid engine, which ran in 2014, had an efficiency rate of 44% and the 2017 unit allegedly produces 109bhp more using the same amount of fuel.
A column celebrating the achievement on Mercedes' official website said "the last time we saw these levels of power in Formula 1 was back in 2005, with a V10 that guzzled fuel at a whopping 194kg/hr" - almost double the fuel-flow rate."