Audi recently conducted its 100th durability test, known as an "INKA" test, on a 2016 A4. INKA is the acronym for Ingolstadt Korrosion und Altern (corrosion and aging). The testing replicates 12 years of vehicle life in 19 weeks.

This corrosion and aging test is conducted in five phases. First, the car is misted with salt and placed in a climatic chamber heated to 95 degrees Fahrenheit. Next up is exposure to a tropical climate with a temperature of 122 degrees and up to 100 percent humidity.

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In the third phase, 80 1,200-watt halogen metal vapor lamps are used to heat the body to a maximum of 194 degrees. The test here is to make sure the materials in the interior don't fade in color or become brittle.

After the heat comes the cold. The fourth phase is meant to simulate polar circle winter conditions. In a chamber cooled to minus 31 degrees, the car is put on a 4-post hydropulse machine that exercises the suspension and rocks the body to simulate the torsion and strain the car experiences on rough roads.

Finally, in phase five, test drivers take the car through specially prepared routesthat include saltwater and mud.

The car is driven only about 7,500 miles, but the punishment it endures is as brutal as 12 years of use.

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After the testing, quality inspectors break the car down into 600 parts and check each for weak points. The Quality Assurance team uses this information to verify a car's corrosion protection and durability and make changes to future models. "The INKA test is an essential tool for assessing the quality of our models and for further optimizing our production methods," said Sylvia Droll, Head of Materials Engineering.

Audi Quality Assurance conducted the first INKA tests in 2002. Since then, it has completed a total of 322,500 hours of testing, driven the cars more than 620,000 miles, and driven through 2,800 mud tests and 1,900 salt tests.

The company's durability testing goes back beyond that, though, as the company's Technical Department has been testing preproduction cars for 40 years.