Few cars carry three distinctions at once. The Mercedes-Benz 300 SLR was the most successful sports-racer of 1955, the machine at the centre of the darkest day in motorsport history, and — in its rare closed form — the most valuable car ever sold. Triumph, tragedy and the auction record, in a single silver shape. Here is the whole story, with the figures verified against Mercedes-Benz and the auction houses.
What was the Mercedes-Benz 300 SLR?
Badged 300 SLR but coded W196 S internally, it was a Grand Prix car in disguise. Mercedes took the 2.5-litre straight-eight from its W196 Formula 1 machine, enlarged it to 2,982 cc, and wrapped it in a two-seat body of Elektron magnesium alloy. The engine kept its most exotic Grand Prix features: a desmodromic valvetrain that closed the valves mechanically rather than with springs, and Bosch mechanical direct fuel injection derived from wartime aero-engine work. It was, in effect, a de-formula'd Silver Arrow built to win on road and track.
| Mercedes-Benz 300 SLR (W196 S) | Detail |
|---|---|
| Built | 1955 — 9 roadsters + 2 Uhlenhaut Coupés |
| Engine | M196 straight-8, 2,982 cc, desmodromic valves, Bosch direct injection |
| Power | ~310 PS (306 hp) at 7,400 rpm |
| Body | Elektron magnesium alloy over a steel tube spaceframe |
| Top speed | ~290 km/h (180 mph) |
| Signature | Hydraulic flip-up rear air brake |
The 1955 Mille Miglia: Moss, Jenkinson and car 722
On 1 May 1955, Stirling Moss won the Mille Miglia — roughly 992 miles of closed public roads from Brescia to Rome and back — in 10 hours, 7 minutes and 48 seconds, at an average of 157.65 km/h (97.96 mph). His car wore the number 722, its 7:22 a.m. start time. Beside him sat the journalist Denis Jenkinson, reading an 18-foot paper roller of hand-written notes taken on earlier reconnaissance, feeding Moss cues so he could commit to blind crests flat out. It was an ancestor of the modern rally pace-note, and the average speed it produced was never beaten: the open-road Mille Miglia was abandoned after 1957. Juan Manuel Fangio finished second in a sister 300 SLR, about 32 minutes behind. Moss called it the finest drive of his life.
A championship in one season
The Mille Miglia was the start of a rout. The 300 SLR also won the RAC Tourist Trophy at Dundrod (a Mercedes 1-2-3) and the Targa Florio in Sicily (a 1-2), carrying Mercedes-Benz to the 1955 World Sportscar Championship by 78 points to Ferrari's 76 — a two-point margin, and all the more remarkable because Mercedes did not finish the season's most famous race.
Le Mans, 11 June 1955
The 1955 24 Hours of Le Mans remains the deadliest accident in the history of motor racing, and the 300 SLR was at its centre. Early in the evening, as the leaders came in for their first stops, Mike Hawthorn's disc-braked Jaguar slowed hard for the pits; Lance Macklin's Austin-Healey swerved to avoid it, into the path of Pierre Levegh's closing Mercedes. Levegh's car struck the Healey and was launched over the low earthen bank into a packed spectator enclosure opposite the pits. Pierre Levegh and more than 80 spectators — some 84 people in total — were killed, and at least 120 were injured. It was the worst toll motorsport has ever seen.
The 300 SLR's Elektron bodywork, chosen to save weight, made a terrible situation worse: magnesium ignites at a low temperature and burns ferociously, and marshals who did not recognise a magnesium fire poured water on it, which only intensified the flames. The race was not stopped — organisers feared that emptying the circuit would block the roads for ambulances. In the early hours, with its cars leading, Mercedes-Benz quietly withdrew them out of respect. Hawthorn's Jaguar won a victory no one wanted to celebrate.
The consequences reached far beyond one race. Mercedes-Benz withdrew from motorsport at the end of its title-winning season and stayed away from top-level racing for more than three decades. Several countries suspended racing while safety was reassessed; Switzerland banned circuit racing outright, a prohibition that lasted for decades. Le Mans itself rebuilt its pit straight. The sport's long, slow turn toward safety began here.
The Uhlenhaut Coupé and the €135 million record
Only two 300 SLRs were ever given closed coupé bodies. They were built for the abandoned 1956 season and, once racing stopped, became the personal transport of Rudolf Uhlenhaut, the engineer behind the car — a roughly 290 km/h company car, arguably the fastest usable closed car of its day. Mercedes-Benz kept both for 67 years. Then, on 5 May 2022, it sold one of them for €135,000,000 — about $143 million — through RM Sotheby's at an invitation-only auction inside the Mercedes-Benz Museum in Stuttgart. It remains the most valuable car ever sold, by a margin that dwarfs the field; the proceeds funded a global scholarship programme, and the car must still be made available for public display. We covered how far it sits above every other result in our guide to the most expensive cars ever sold at auction.
Why it still matters
The 300 SLR is the rare object whose value is inseparable from its history — the wins, the loss, the withdrawal, the record. Cars like this stop being machinery and become fixed points, the shapes collectors and artists return to again and again, alongside the Ferrari 250 GTO and the Lamborghini Miura. Few of them, though, carry quite so much in a single silver body.
Frequently asked questions
Why is the Mercedes 300 SLR so valuable?
Extreme rarity (only 11 were built, two of them the unique closed coupés), a dominant 1955 competition record, and Mercedes-Benz's 67-year ownership of the coupés. One coupé sold for €135 million (about $143 million) in 2022, the highest price ever paid for a car.
What happened at the 1955 Le Mans disaster?
A braking incident launched Pierre Levegh's 300 SLR into the crowd. Levegh and more than 80 spectators — around 84 people in total — were killed and at least 120 injured, the deadliest accident in motorsport history. Mercedes-Benz withdrew from racing for over 30 years afterward.
Who drove car 722 in the 1955 Mille Miglia?
Stirling Moss, with navigator Denis Jenkinson, winning in a record 10 hours, 7 minutes, 48 seconds at 157.65 km/h — a mark never beaten.
How fast was the 300 SLR?
Around 290 km/h (180 mph), from a 2,982 cc straight-eight producing roughly 310 PS — extraordinary figures for 1955.
