On 5 August 1888 and without her husband's knowledge, she drove her sons, Richard and Eugen, fourteen and fifteen years old, in one of Benz's newly-constructed Patent Motorwagen automobiles—from Mannheim to Pforzheim—becoming the first person to drive an automobile over more than a very short distance. The distance was more than 106 km (more than sixty miles).
Although the primary purpose of the trip was to visit her mother, Bertha Benz also had another motive: to show her brilliant husband—who had failed to consider marketing his invention adequately—that the automobile would become a financial success once it was shown to be useful to the general public.
Underway, she solved numerous problems. She had to find petrol or similar fuels which were available—sometimes—only at dispensing chemists' shops. A blacksmith had to help with a chain at one point. Brake linings needed replacement. Bertha Benz had to use a long, straight hairpin to clean a fuel pipe which had become blocked and to insulate a wire with a garter. She left Mannheim around dawn and reached Pforzheim somewhat after dusk, notifying her husband of her successful journey by telegram. She drove back to Mannheim the next day.
Along the way, several people were frightened by the automobile and the novel trip received a great deal of publicity—as she had sought. The drive was very helpful for Karl Benz, as he was able to introduce several improvements after his wife reported everything that had happened along the way—and she made important suggestions, such as the introduction of an additional gear for greater ease climbing hills.
Mrs Benz passed away in 1944 aged 95.