Diniz entered Formula One, the highest category of circuit racing defined by the Fédération Internationale de l'Automobile (FIA), motorsport's world governing body, with the Forti team, as team-mate to Roberto Moreno in 1995. In addition, this was the first of a three-year contract with Diniz and his backers. Despite his lack of success in F3000, he was guaranteed a seat as his family and sponsors were paying a significant amount of the team's budget. Furthermore, retired driver René Arnoux was employed as a consultant and driver coach for Diniz. The season started with Diniz scoring three consecutive finishes, albeit outside of the points scoring positions—but was not classified for the races in Argentina and San Marino. He did not finish the next race in Spain due to a gearbox problem and finished tenth in Monaco. Diniz retired from the next five races he entered, primarily from car issues and spun off into retirement at Magny-Cours. He subsequently finished every remaining race of the season, apart from the Grand Prix held at Suzuka where he spun off. He finished the season scoring no points and was unclassified in the Drivers' Championship. Diniz's good finishing record enabled him to establish himself as a steady, dependable driver. In December, Diniz signed for the Ligier team for 1996, despite team owner Tom Walkinshaw initially refusing to hold talks with the Brazilian driver. Ligier eventually signed Diniz after a shootout test session against other drivers in which Diniz was the fastest, also impressing the team with his approach and technical feedback. At the end of the season, Diniz and his sponsors were described as "throwing their money away" on the uncompetitive Forti. But the more significant impact of his first year in F1 was that the Brazilian had done nothing to assuage critics who had said he was a "pay driver". It took him several years to prove that he was not just in the sport because of his funding.