The Austro Engines full takeoff power (100% load) is limited to 5 minutes (like almost every other aircraft, including jets), maximum continous power 92% load.
The older Thielert engines allowed 100% load continous operation.
Note: The RPM on the engine display refer to propellers RPM.
DA42 NG (Austro) Aircraft Flight Manual
DA42 TDI (Thielert) Aircraft Flight Manual
An even newer version of DA42 consumes as little as 13 L / 100 km or 18 MPG statue (jet fuel) at 155 KTAS (287 km/h or 178 mph TAS) and high altitude.
At maximum continous power (92%), about 17.3 L / 100 km or 13.6 MPG statue at about 190 KTAS (352 km/h or 219 mph TAS) at FL160 (4.88 km).