Engel took the start after earning pole position with a record-breaking 2:00.8819s in final qualifying on the afternoon prior at Mount Panorama.
The Safety Car led the field away for what was the official start at 05:45 local time/AEDT in cool temperatures, and remained there for two laps rather than one.
It was then left for Engel to take the green flag for the commencement of what was officially Lap 3 just after 05:54, with the field in single file.
Luca Stolz sat fourth in the #75 SunEnergy1 Mercedes-AMG entry which won the race last May, from Augusto Farfus in the #46 Team WRT BMW.
After a clean start and one green flag lap in the books, Engel's margin over fellow German Gotz was just 0.3593s, with Preining several tenths further back.
First of the Pro-Am runners was gentleman driver Liam Talbot in sixth outright in the #65 Melbourne Peformance Centre Audi which Chaz Mostert had qualified, running a few seconds back from Farfus in the opening stages of the once-around-the-clock race.
A total of 24 cars took the start, with #66 Daytona Sports Cars SIN R1 officially withdrawn after an incident in practice on Saturday morning.
Through six practice sessions and three qualifying sessions, the Mercedes-AMG has looked the vehicle to beat, and so it was that SRO hit them with an extra 10kg in pre-race BoP changes.
The Manthey EMA Porsche which started from third is also carrying 5kg of extra weight, while the three other GT3 models in the field have all had weight removed.