Mercedes is keeping their biggest car changes a secret for now, but more engine gains have been confirmed for 2021.

Once again, the Brackley-based team enter a new season as favourites to win both championships for what would be an eighth consecutive year.

But the grid is expected to be closer as teams were given just two development tokens to make significant changes, while other parts of the car were frozen completely. 

"What's carried over will be different from team to team, because the rules didn't require you to carry over the same things," Mercedes technical director James Allison explained.

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"The only thing we can say with certainty at this stage is that everybody's cars will have significant areas that are the same as their 2020 car but those areas will vary from car to car, depending on how they chose to spend their tokens.

"In addition, there are some parts of the car that you can change token-free, for example, the power unit, the cooling systems, the suspension and of course all of the aerodynamic surfaces.

"We have spent our tokens, but we won't reveal how we used them just yet. That'll become clear in good time."

Mercedes have had to make one key change for 2021, that being the removal of their innovative DAS system, which helped drivers warm up the front tyres by changing the toe angle by pulling on the steering wheel but has been outlawed for this year.

Also notable was a reshaped sidepod design which is now so tight that a bulge has appeared towards the rear to accommodate the power unit.

And as for the engine, Mercedes has no problem in admitting more progress has been made to their benchmark design both in terms and performance and particularly reliability.

“We’ve continued the development of the technology in the power unit,” engine boss Hywel Thomas was quoted by The Race.

“That’s a continuous process, and we feel like we’ve been able to take a step forward on that front again this year.

“The second area is reliability. We discovered some design issues last year, so we’ve been looking at those and introduced some changes to address them.

“And we’ve also got some completely new innovations that will be in the racing PU for the first time."

A notable change is an actual reversal of changes made to the MGU-K last year, which resulted in several failures toward the end of the year and forced Mercedes to turn down its performance in Abu Dhabi.

“We introduced a complete redesign in 2020, a very different MGU-K to what we had run previously,” Thomas explained.

“It helped us make a solid step forwards in performance, but it was a design that turned out to be difficult to manufacture and assemble consistently.

“We had lots of examples where the MGU-K ran a full cycle and did exactly what we wanted it to do, but we also had some cases of midlife failures.

“For 2021, we’ve gone back, looked at that design and built an understanding of where the failures have come from.

“We have changed it for this year, to allow for a more consistent manufacturing route which should help to improve the reliability of the MGU-K.”

Worrying news if you're Red Bull that's for sure...