Mercedes-Benz has set the standard so far in the hybrid era. So, where has the focus been over the winter to maintain that level of performance?
"It's been more of the same," says Managing Director, Mercedes AMG High Performance Powertrains, Andy Cowell. "To get the performance out of this new generation of Power Units, you need to chase efficiency. That's both combustion efficiency and efficiency in the various energy transition steps - i.e. MGU-H, MGU-K, turbocharger, power electronics and batteries. We're constantly working on every single piece of the puzzle to improve performance at the crankshaft, while also seeking to ensure we don't suffer any of the problems we had last year with reliability. So, it's about getting down to the root cause of issues and making sure that everything is robust across our whole process, as much as extracting performance.
"These Power Units really are incredible feats of engineering. We're now running at more than 47% thermal efficiency and producing historic highs of power - and all with an ICE restricted to consuming fuel at a rate of just 100kg/hr. The old-fashioned, naturally aspirated engines peaked at 29% thermal efficiency during the V8 era - while the last time we saw these levels of power in Formula One was back in 2005, with a V10 that guzzled fuel at a whopping 194kg/hr. To halve the fuel flow rate for the same amount of power is quite something."
And with 32 tokens available to spend across the winter and during in-season development, the scope for development is significant...
"32 tokens is quite a lot," continues Andy. "So we haven't had to restrict any of our development activity to a specific area. Anything which could yield a decent efficiency improvement - and therefore a decent performance improvement - has been explored and we're now working to make sure our package is sufficiently durable in time for Melbourne. "
An extra two races on the calendar means an increased Power Unit allowance for the season ahead. But how will this affect the team's approach to 2016?
"On the face of it, an increased allocation of Power Units would seem to give manufacturers an advantage, in that each unit is required to complete fewer races, thereby putting less pressure on the life cycle of different components," says Andy. "But the reality is that our durability targets have remained the same. Our target is to make sure that each Power Unit can last for at least five races, meaning that theoretically we only need to use four per driver, across the season. We believe this gives us a good opportunity to react if we have a reliability problem - or potentially to use the extra units to our advantage for a performance enhancement at key races.
"The upgrade that we introduced in Monza last year took a huge amount of effort from the factory at Brixworth and we only had enough resource to supply the works team with the latest spec at that time. However, that is now paying off for every team with Mercedes power, as we've managed to build on that development work through the autumn and winter period. Now, all our customers are getting an improved package that is exactly the same specification as the works team. All eight Mercedes powered cars will have exactly the same hardware and performance potential come Melbourne - which is a good step for everyone."
Fuel and lubricants were central to that development step. But how central will the role of PETRONAS be in finding yet more performance from the Power Unit?
"The rate of development from the Power Unit over the past two years has been very impressive," Andy continues. "Many people thought that there was not much opportunity to move things forward - but that has not been the case. There have been significant new advances - and fuel and lubricants have been one of the main focus areas. Our 2015 mid-season update incorporated a sizeable step in fuel performance from PETRONAS. Then, later on in the year, we also introduced a new lubricant. We've made further progress in the way we've designed the combustion system and also enhanced the properties of the lubricants to reduce friction in the engine. PETRONAS are a key partner for us. They're not just branding on the car - but a deep-rooted technology partnership. Anybody who designs engines knows that good fuel and lubricants are key to performance - and we're very fortunate to have such a close and productive working relationship with PETRONAS."
Noise has been a hot topic since the new Power Unit formula was introduced in 2014. But what's changing in 2016 to pump up the volume and will this have any effect on performance?
"We've been conscious since the start of the Hybrid era in 2014 that the volume has diminished for those up in the grandstands as well as those watching at home," says Andy. "This is down to both the nature of a turbocharged engine and the recycling of waste energy in the exhaust system. The FIA therefore undertook an interesting and thorough investigation to analyse noise in the tailpipe and investigate what could be done to increase noise without impacting performance or efficiency. What they spotted is that the waste gate fed into the tailpipe. So, when the waste gate is not open, it's a dead end. It then becomes a side branch resonator - or effectively a silencer - on the tailpipe. That design has now been removed, so we are left with a nice clean pipe without any silencing points, which should improve the noise of the Power Unit."