The S-Class has had some rocky iterations over the years – from the W140’s troubled birth into a hostile, more eco-conscious world that was in recession, to the out-of-warranty nightmares of the millennial models that followed – but it still remains the car against which all executive cars are judged.
It may no longer be the true top-of-the-tree either – that’s reserved for Maybach-monikered machines – but for the plutocrat in a hurry, there are few better places to plot your next merger or acquisition than in the back of an S-Class.
There are many S-Class stories from history – the infamous Red Pig taking second at Spa Francorchamps in 1971, to the wild AMG-tuned monsters that served as an engine precursor to the Pagani Zonda. It’s always been a pioneer in safety and technology, with airbags, stability control and a whole heap more making its debut on the model – now these are in every new car.
However, there is one S-Class model that deserves to be held aloft as one of the best, if not the best versions – and that is the W116 450 SEL 6.9, which celebrates its 50th birthday in 2025.
Its origins begin with the flagship 600 limousine, and in particular its M100 V8 engine. In 1966 company engineer Erich Waxenberger came up with a plan to transplant said M100 V8 into the much lighter 300 SEL W109 – a weight saving of around 1300kg. Considering the 6.3-litre V8 made 247bhp, the effects were dramatic. According to company legend, one test driver, upon burying the throttle, had to jump out of it in disbelief.
The car was eventually released in 1968 and did much to improve the performance credibility of Mercedes-Benz of the time. The follow up, however, would be punchier still.
The W116 was a huge leap forward for Mercedes-Benz, in technology, styling and range. It was Friedrich Geiger’s last design for the company, and would go on to influence the brand’s styling for at least a decade.
A range of V8s were offered straight off the bat, with the 4.5-litre M117 offering around 220bhp and 278lb ft of torque – quite chunky for the time, you might have thought. But Mercedes-Benz thought differently, and it soon started developing the 450 SEL 6.9.
Despite the naming, the engine actually displaces 6834cc, enough to make it the largest-engined European engine since before the Second World War, and the largest then built by Mercedes-Benz. In order to get the vast unit to fit below the bonnet line, the engine uses dry sump lubrication to lower the engine height. This necessitated a much larger oil capacity – 12 litres rather than the standard five litres on the M117, and moving the dipstick.
The grand total of these changes in horsepower terms? 286bhp. Still a lot for 1975, but one might argue that the vastly cheaper M117 V8-engined was ‘enough’ for a luxury barge. But you’re forgetting the torque…
The 450 SEL’s 4.5-lire engine produces an admirably chunky 278lb ft at 3000rpm. The 450 SEL 6.9, meanwhile, produces a stump-pulling 406lb ft at 3000rpm. To put that into perspective, the Ferrari F40 produces just 20lb ft more…
This meant that the 450 SEL 6.9 reigned supreme as the fastest four-door saloon for many years, despite weighing 1985kg. It could hit 62mph in 7.4 seconds and top out at 140mph. To put that into perspective, the Ferrari 308 GTB, launched the same year, was only around half a second quicker to 60mph.
The engine wasn’t some highly strung affair – the huge oil reserves pushed changes to more than 12,000 miles, and the hydraulic valve clearance compensation mechanism no longer meant expensive periodic adjustments. The cylinder head gasket was designed so that the head itself didn’t need to be retightened. It was hugely fast, but strong too. The three-speed automatic gearbox was derived from the standard W116, but beefed up to cope with the vast torque reserves of the 6.9.
However, there’s far more to the 450 SEL 6.9 than its magnificent engine. Unlike other W116 models, which used hydropneumatic self-levelling suspension at the rear only as an option, the SEL 6.9 used the system all-round. Unlike Citroën’s take on the theory, the SEL 6.9’s timing chain drives the hydraulic pump, with separate pumps for the brake boost, power steering and suspension system. This set up introduced extra failsafe over Citroën’s rubber belt/single pump method; Mercedes-Benz also added hard rubber dampers as temporary springs if the system failed. The Mercedes system also differed in having its system maintain body level without squatting or diving during acceleration or braking; however, it doesn’t sink to the ground like the Citroën system.
The SEL 6.9 is also notable as being the world’s first passenger car to be fitted with anti-lock brakes (in the style we now know it). Produced in association with Bosch, it worked on all four wheels via a four-wheel electrical system; it was introduced in 1978.
It was all set up to be a massive signal of intent to the world about the mighty Mercedes-Benz – but then the 1973 oil crisis hit. Mercedes-Benz chose to delay the launch, and had pretty much given up on the North American market due to harder emissions regulations. However, such was the demand from dealers and customers, it finally came to market in 1975.
At the 6.9’s debut, Professor Hans Scherenberg, Member of the Board of Management of what was then Daimler-Benz AG and Head of the Overall Development and Research department, said: “As the S-Class’s top-of-the-line model and successor of the 300 SEL 6.3 with air suspension, the 450 SEL 6.9 has the potential to live up to the demands of our most spoilt contemporaries.” Talk about understatement.
Then again, if you’d come to the car from a Rolls-Royce or a Bentley, you might have felt a bit let down inside. Other than burr walnut veneer, the height adjustment knob and some extra warning lights for the suspension, and the options for heated seats and an electric sunroof, it looked just like the standard W116. Though smart, it was hardly the height of luxury living in the Bentley/Rolls-Royce vein – instead, you were buying the luxury of engineering integrity. However, the fitment of a fully automatic air conditioning system – the first for a Mercedes-Benz – certainly helped keep you cool. Adapted from a Chrysler unit, the compressor was sourced via General Motors.
Nevertheless, the SEL 6.9 proved to be comparatively popular, given the difficult sociopolitical times of the late 1970s – 7380 left the Sindelfingen works between 1975 and 1980, despite it being more than twice the price of a bottom-of-the-range W116 280S.
Its incredible performance has led to many legendary stories, largely as it attracted the wallet of many incredible people. James Hunt had one, which spent most time up on bricks as he couldn’t trust himself to keep within the letter of the law, or within the realms of his bank balance due to the fuel economy.
Writer LJK Setright found out about the fuel economy during a 124.3-mile autobahn trip with development engineer Erich Waxenberger. Apparently the SEL managed 11mpg on the trip, which took precisely one hour and 10 seconds.
Then there was the time Juan Manuel Fangio was demonstrating the car around Silverstone, with three journalists onboard. Mid conversation, he ended up blasting past a flat-out racing De Tomaso Pantera, with a dollop of opposite lock – one handed.
Clearly the car struck a nerve with racing Argentinians, as my favourite story is alleged to have been about Carlos Reutemann. Asked to act as a medical car driver in his 6.9 for an F3 race in Brazil, he asked the organisers how fast they wanted him to go. They said “as fast as you like, you won’t catch them”. By the end of the first lap, he was mid-pack.
Such abilities also led to the car becoming a legendary screen star. Its most notable appearance was in Ronin, in which it played a prominent role in its chase scenes; the standing burn-out and then being used as a missile platform being two scenes of particular note. It also played a key role in David Lynch’s Lost Highway, tying together the film’s male characters – in that, it was said to have had a 1400bhp engine conversion, which allowed the car to push a Ford Thunderbird off the road despite it having the brakes on.
However, it is in Claude Lelouche’s C’était un Rendez-vous that the 450 SEL 6.9 proves its worth. Though it sounds like a Ferrari 275 GTB being driven, the mixture of high torque, anti-lock brakes and smooth suspension meant the 6.9 was perfect for getting the shots Lelouche needed.
My own experience with the 6.9 wasn’t quite as frantic – but it was memorable. I was loaned one for a couple of weeks, and in that time I covered 180 miles, at a cost of £180.
Perilous finances aside, it was a truly memorable experience. The gearing is such that you can hit more than 60mph in first gear, while second appears at a little more than 100mph. However, it is the way that it builds this speed – unless you bury your foot harshly, there’s pure linear acceleration all around the dial, with imperceptible gear changes.
Experiencing that on a runway was memorable for other reasons – namely that this particular example wasn’t in the finest fettle. With the encouragement of the owner, we decided to see just how close to 140mph it could get.
Despite being more than 40 years old then, it got to 135mph, which is when the engine started to cough due to fuel starvation. Oh, and the rust on the wings was starting to break free and hit the windscreen…
The 6.9 is more than a car – it’s a folk hero, a reminder of a time when bigger was always better. Later Mercedes-Benz engines would be more powerful still, and far more efficient, but trust me – there’s nothing like blasting past a hitherto smug modern Audi driver in a rusty old Mercedes at high velocities…
See more:
Buying Guide: Mercedes-Benz W116 S-Class (1972–80)
Was the W140 S-Class the Last “Proper” Mercedes-Benz?
Gullwing Turns 70: The Iconic 300SL “Is Mercedes-Benz”
