Germany have so far failed to recapture their dazzling form of 2010 when they finished third in South Africa, claiming the scalps of England and Argentina en route.
But Löw says the best is yet to come as they bid to beat France and claim a place in Tuesday's semi-final against either Brazil or Colombia.
"You either win and stay or lose and go home," Löw said in a blunt appraisal of the upcoming game at Rio de Janeiro's Maracana stadium, mindful of his team's patchy showing in Brazil.
"We haven't shown a consistent level of performance so far," said the 54-year-old coach. "Teams like Ghana and USA had nothing to lose and everything to win, this game is different."
But seven of the German team have shown signs of ill-health this week, Löw added.
"One third of our squad were complaining of sore throats and perhaps they picked something up from the air-conditioning and different climates here," the coach told journalists Thursday, but without over-dramatizing the situation or naming the affected players.
"Sometimes you have to wait and see how things develop."
The German FA (DFB) had previously said defensive midfielder Christoph Kramer is struggling to be fit for the Rio clash after showing flu-symptoms.
Centre-back Mats Hummels already missed Monday's last 16 win over Algeria with illness.
The Borussia Dortmund star tweeted on Wednesday that he is "almost 100 percent" ready to face the French.
But Germany goalkeeper Manuel Neuer on Thursday revealed Hummels had been kept away from his team-mates at the team's hotel to stop the bug from spreading..
However, the full squad trained at the Maracana stadium on the eve of the game with no obvious ill effects.
The match will be the first competitive meeting of the nations since West Germany beat France 2-0 in the 1986 World Cup semi-finals, four years after they also triumphed on penalties when the teams met at the same stage of the competition in Spain.
While France coach Didier Deschamps though Deschamps accepts that Germany are the strongest side they have faced yet at these finals, he said the team was relaxed and ready for the challenge.
"We have no pressure on us, just excitement at being able to play a World Cup quarter-final. We will have a new page of our history to write and let's hope it is a beautiful one," said Deschamps, whose side edged past Nigeria with a 2-0 victory in the last 16 on Monday.
Löw, meanwhile, is bidding to steer his side to the semi-finals of a major tournament for the fourth consecutive time in his eight-year reign.
Germany have failed to impress since thumping Portugal 4-0 in their opening match.
The team finished as group winners after grinding out a 2-2 draw with Ghana and a 1-0 win over the USA, but laboured to a 2-1 extra-time win over Algeria on Monday in the last 16 after struggling to finish their chances.
"We have not yet delivered our best possible performances, " Löw said.
There is plenty at stake in Rio on Friday, but that has not prevented the sides from engaging in some pre-match banter.
Ahead of the game, German football federation (DFB) president Wolfgang Niersbach consulted with France's UEFA chief Michel Platini about the best formula for a German victory on Friday.
"I sent him an SMS and quickly asked for a tip on how to beat the French," Niersbach said. "He rang me back and told me that we just have to score one goal more…"