Father Arthur Dontje supported his sons Indy and Milan with their own karting team early in their careers. Arthurs chocolate company, Dobla, was the naming sponsor. Indy started racing in Rotax Max powered classes, such as MiniMax and Junior Max.[1] After graduating into shifter karts, Dontje raced in the German Karting Championship in 2009 against other young hopefuls such as Jack Hawksworth and Hannes van Asseldonk.[2] Later in his karting career, in 2010 and 2011, the young karter competed in the USA in the SKUSA SuperNationals. In 2010 Dontje finished third in the S1 class.[3] The following year Dontje finished second in a factory supported Energy Corse kart.[4]
Single seaters
Dontje made his single-seater debut in 2012 at age 19. Racing in the ADAC Formel Masters Dontje joined Team Motopark, part of the Lotus F1 junior program.[5] During the season Dontje scored one podium finish, a third place at the Sachsenring.[6] For 2013 Dontje remained at Team Motopark. He won the third race of the season, at Motorsport Arena Oschersleben.[7] The Dutchman won a second race at the Red Bull Ring.[8] Dontje was the only driver to score points every single race during the season. This placed the Dutchman sixth in the series standings.
For 2014 Dontje remained at the Lotus backed Team Motopark to race in the ATS Formel 3 Cup.[9] With the German F3 championship running older machinery compared to the European F3, the German championship struggled to attract many drivers with many races being run with less than ten drivers. Dontje scored fourteen podium finishes, with a single victory, out of 23 races. Dontje won the second race during the Red Bull Ring weekend.[10] The Dutchman also competed in the 2014 Zandvoort Masters. Dontje challenged Nabil Jeffri for third but had to settle for fourth place, scoring the fastest racelap in the progress.[11]