The 1927 Grand Prix season was the third (and final) AIACR World Manufacturers' Championship season and the second run to a 1.5-litre engine limit. In a dominant display, the championship was won by Delage, with team driver Robert Benoist winning four of the five Grand Prix.
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The championship opened with the Indianapolis 500 – once again a contest between Duesenberg and Miller engines. Previous year's winner Frank Lockhart started on pole position and led for over half the race until his car suffered a broken con-rod. Rookie George Souders, driving Peter DePaolo’s 1925 race-winning Duesenberg, came through and took a comfortable victory with an eight lap margin. DePaolo went on to secure the season's AAA Championship with three wins and four second places.
After major re-working over the close season to sort out the chronic exhaust and heating issues, the Delages proved unbeatable. They were the only manufacturer to enter the requisite three races to qualify for the championship. Bugatti and Talbot challenged them at the next Grand Prix, in France, but then the Talbot team was shut down. Three Americans, including Indy-winner George Souders, came over for the mandatory Italian round but their oval-track car-designs were unsuitable for European circuit-racing. The final round, the British Grand Prix attracted a bigger field, but once again Delage was able to romp to a dominating 1-2-3 victory.
It was already readily apparent that the 1.5-litre formula was not attracting consistent manufacturer interest. The AIACR had stated, before the season started, that from 1928 it would not continue this racing format but instead run its Grands Prix to an open Formula Libre, as most other European races were already being done.
The season had opened with the advent of a new road-race across northern Italy – the Mille Miglia was a race for touring cars from Brescia to Rome and back. Ferdinando Minoia led home a triumphant 1-2-3 for OM. In a rain-affected Targa Florio, Emilio Materassi kept control to win for Bugatti. His success continued and he went on to be the winner of Italy's inaugural Driver's Championship. The other significant event of the racing year was the opening of a major new racetrack in Germany. The Nürburgring was over 30 km of winding road with 172 corners, situated near the Ardennes Forest just across the border from the Belgian Spa-Francorchamps circuit. The opening race in June was won by Rudolf Caracciola in a 6.8-litre Mercedes sports-car.