For the first time in Grand Prix history the ACF mandated an engine capacity limit — 4.5 litres maximum — alongside a weight range of 800–1,100 kg. The rule was designed to rein in the enormous displacement engines that had come to dominate racing and to give smaller, more technically sophisticated manufacturers a fair chance. Entry was capped at five cars per constructor, with no privateer entries permitted.
The Lyon circuit ran clockwise across public roads, passing through the Gier valley and featuring the notorious switchback nicknamed "le piège de la mort" — the death trap. The race was set at twenty laps, totalling 752.6 km.
Peugeot arrived as strong favourites on the strength of their 1912 and 1913 victories. Their new EX-5, carrying a 4.5-litre twin-overhead-cam four-cylinder producing 112 bhp, was driven by Georges Boillot, Jules Goux, and Victor Rigal. Four-wheel brakes gave the Peugeots a handling advantage that Boillot had tested at Brooklands, along with a streamlined extended tail to raise top speed.
Mercedes entered five of their new 18/100 cars, developed with input from the aero-engine division. A single-overhead-cam unit with four valves per cylinder produced 106 bhp at 3,100 rpm. The team retained experienced drivers, led by Christian Lautenschlager — winner of the 1908 French Grand Prix — alongside Louis Wagner, Otto Salzer, Max Sailer, and Théodore Pilette.
The field of 37 starters from 13 manufacturers and 6 countries also included Sunbeam, Delage, Opel, FIAT, and Vauxhall, with American Ralph DePalma among the Vauxhall entrants.
Conditions were hot and fine, with approximately 300,000 spectators lining the roads. Cars departed in pairs at 30-second intervals from 8am. Boillot was first on the road after the opening lap but Sailer's Mercedes led on elapsed time. Sailer forced an aggressive pace, drawing Boillot into a speed battle, but on the sixth lap he retired with a broken connecting rod after pushing his machinery too hard.
From lap seven Boillot held the lead, managing his advantage carefully over the opening half. Tyre wear proved decisive: Boillot's Peugeot on Dunlop rubber required six pit stops for tyre changes against a single stop for the Mercedes cars running Continental tyres. Despite Boillot's exceptional driving keeping him ahead, Lautenschlager's relentless pursuit closed the gap. On lap 17 Lautenschlager overtook the Peugeot at Givors. Boillot's engine, by now running on three cylinders, expired on the final lap on the climb out of the Gier valley. Boillot was found hunched over his steering wheel, weeping.
Mercedes finished 1-2-3: Lautenschlager ahead of Wagner and Salzer, with Jules Goux fourth for Peugeot nearly ten minutes back.
Within a month of the race, Europe had descended into World War I and Grand Prix racing ceased for four years. Boillot transferred to the French Air Force as a fighter pilot and was shot down over Verdun in April 1916.
The technical ripple effects of the race were considerable. Rolls-Royce engineers, having acquired and dismantled one of the Mercedes Grand Prix cars in London, incorporated the SOHC valve train design into the Rolls-Royce Eagle aero engine, which subsequently powered Bristol fighter aircraft. Ralph DePalma purchased one of the Mercedes cars and used it to win the 1915 Indianapolis 500. The Peugeot EX-5 cars were also exported to the United States, where they competed at Indianapolis in 1915 and 1916.
The 1914 French Grand Prix stands as a defining moment in early motorsport: the race that demonstrated German engineering precision overcoming French flair on the cusp of catastrophe, the last great pre-war spectacle before a continent-wide silence fell on the sport.