Mercedes boss Toto Wolff has a sense of dread ahead of this weekend's Austrian Grand Prix.

The Brackley-based team should be full of confidence after Lewis Hamilton dominated last Sunday's race in France, with Valtteri Bottas giving them a sixth 1-2 of the season.

However, last year, the Red Bull Ring saw the rarest of rare things as both drivers would retire due to mechanical issues and though results have still been good, the W10 hasn't been flawless in recent races.

"Our result in last year's Austrian Grand Prix was the low point of the 2018 season," Wolff said ahead of what is his home race.

"A double DNF after a promising front-row lockout meant that we left a lot of points on the table and the race was a cruel reminder of how quickly things can go wrong in our sport and that reliability and performance go hand in hand in Formula 1.

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"This year, our race finishing record has been good, but it would be complacent to ignore the fact that for two weekends in a row now, our mechanics had to perform the equivalent of 'open-heart surgery' on our cars.

"We've faced a number of different issues on different components, each of which could have easily caused us to retire, so we need to get on top of those challenges as quickly as possible."

Some of the niggles included a spark plug failure on the engine inside Lance Stroll's Racing Point as well as a hydraulic leak on Lewis Hamilton's car in Canada.

Then at Paul Ricard, Valtteri Bottas' last seven laps were hindered by a misfire from his power unit.

Not helping the Mercedes boss' worries is the weather expected in Austria as a heatwave makes its way across Europe.

"The forecast for Austria predicts temperatures of 30 degrees Celsius and more which, combined with the reduced air density owing to the track's location at altitude, means that cooling could become a real challenge in Spielberg," Wolff noted.

"Add to that the short lap and the close gaps on that circuit and our direction is clear: we need to keep working diligently, stay humble and give it everything to do a better job than we managed 12 months ago."