Curbside Classic: 1971 Mercedes-Benz 300SEL (W109) 6.3 – The Car, The Myth, The Legend

Benz-wise, the year 2022 will forever be the year of the 300 for yours truly. This year, I found and wrote up a W109 300SEL 3.5 saloon (utterly beautiful) and an ultra-rare mid-‘60s W112 300SE Coupé. Time to complete the 300 trifecta with the absolute star of the show, the “greatest sedan in the world” and arguably the most incredible Q-car ever made: the 6.3 litre 300SEL.

It’s a wonder that the 6.3 is only making its CC debut now, in a way. Sure, they’re pretty rare – only 6526 units made over five years – but they are beyond iconic and quite a few made their way across the Atlantic, so one would have thought one of these would have had its day on CC already by now. Not the case, no problem; Tokyo will provide.

Where to start on such a legend? First with the looks, perhaps. Let’s go full-on Biblical. In the beginning (a.k.a. 1959) was the Fintail. And the world thought it was good, but maybe could be even better. On the second day (1961), Paul Bracq penned the W111/112 two-doors, and the world said “Ooooh!”, and on the third day (1965) he designed the W108/109 saloon and the world went “Aaaah!” The definitive Mercedes-Benz shape was made.

Underneath, the W108/109 was also a direct descendent of the W111/112. The wheelbase remained identical – 2750mm for lower-spec W108s, an additional 100mm for higher-spec W108s and W109s, which were all longer “SELs,” unlike their W112 forbears. The swing axle rear end, a Mercedes mainstay since the late ‘20s, was kept on for one last go. W109s inherited the W112’s complex air suspension and its fuel-injected 3-litre straight-6, as well. The only significant change was the replacement of the Fintail’s rear drum brakes by discs.

The venerable M186 straight-6 had served Mercedes well, since its 1951 debut. It had powered the stately 300 “Adenauer” limos, the legendary 300SL, the elegant 300 S/Sc, the superlative W112s… It was never mated to the Pontons, which I feel is another point in its favour (I don’t like the Ponton). But by the mid-‘60s, the 3-litre’s time was running out. Mercedes were busy working on a pair of V8s, a 3.5 and a 4.5 litre with EFI, which not going to be ready for action before MY 1970. In the meantime, to take over luxury car duties, a 2.8 litre variant of the M108 straight-6 was devised, shared by the W108 and W109 (and the late model Pagodas) from late 1967 onward.

Mercedes-Benz 300SEL 6.3 German brochure excerpt, 1971


But the expected 3.5 and 4.5 litre engines were not the first V8s Mercedes ever made. In 1963 (I guess that would be the fourth day, which came before the third, but that’s just one of those quirks of scripture), M-B had shocked the world by launching the 600 (W100) limo, the sum total of all the technological sophistication that the company was able to muster into a single vehicle. And to give that behemoth sports car performance, Mercedes engineers created a 6333cc OHC V8 with an in-house mechanical fuel injection that churned out 250hp (DIN).

This M100 engine, as it became known, was mated to a Mercedes-made 4-speed automatic. There just wasn’t a manual gearbox around that could take on the job. But let’s return to the silly Biblical theme and get to day five, in 1966, when Mercedes-Benz test engineer Erich Waxenberger was berated by a journalist friend of his for building “granny cars and taxis.” That barb got under Waxenberger’s skin, so he procured a reject W109 body from Sindelfingen and shoehorned the 6.3 litre V8 in there, just to see if the result could be made to work coherently.

Famously, the prototype was made completely without knowledge or approval from the Daimler-Benz top brass. Waxenberger was a bit of a maverick, test-driving cars beyond their intended design briefs and relentless in his efforts to iron out defects as he found them. He was protected by M-B racing director Rudolf Uhlenhaut, who said of the engineer “I’m just glad to have somebody who can push our cars to the limit.”

One evening, Uhlenhaut heard the Waxenberger W109 burbling past his window. He immediately asked to be allowed to take a test drive, which Waxenberger managed to delay to the next day. A small team of mechanics and engineers worked through the night to gussy up the car and fine-tune it as much as possible. Uhlenhaut was very impressed with the results, soon taking the prototype on a long-distance European jaunt, just to gauge the car’s everyday usability, which seemed quite satisfactory. Once Uhlenhaut was on board, the notion of actually building that monster and selling it started to take root.

Production got under way in December 1967, but the 300SEL 6.3’s grand entrance only took place at the Geneva Motor Show in March 1968. Immediately, the new Benz’s price, displacement, performance and refinement placed it at the apex of the range, just under the plutocrat/rock star/head-of-state chariot that was the exclusive 600. It had nearly all the trappings of the Grosser, but half the ostentation. Hence the 300 number, one can only surmise.

The 300SEL 6.3 came fully-loaded: power brakes, steering and windows, leather or velour upholstery, genuine wood veneer, central locking, self-levelling air suspension, automatic gearbox… and a golf driver-shaped wooden gear selector, though that one might just be for this particular car. Ditto the steering wheel, of course. Period optional extras included power sunroof, radio with power antenna, A/C, radio-telephone, a luggage set and whatever shade of woodgrain one could want.

This is the ultimate incarnation of the classic autobahn cruiser, able to make five adults float above the asphalt at over 200kph in safety and comfort for hours – or whenever the 105-litre petrol tank starts showing signs of running dry.

When production was finally halted in September 1972, the 300SEL 6.3 had blown all expectations. As I said at the start of this post, only a little over 6500 units were made, which isn’t much compared to Cadillac or Lincoln. But compared to the Rolls-Royce Silver Shadow, which is arguably much closer to the Benz than anything Detroit had to offer, it’s a pretty great score. And it represents about a third of all W109s. Considering the minimal expense Daimler-Benz had to risk to design and produce the car, the 300SEL 6.3 was all gravy for Mercedes. The 300SEL 6.3 beats the Silver Shadow in nearly all respects, frankly — performance, handling, reliability, looks, sophistication. I’d say the only area where the Benz is bested by the Brits is, in my view, the Roller’s warmer cabin atmosphere and its sense of exclusivity. But not everyone wants do display their wealth so blatantly.

Fifty years on, the main challenge with these outstanding machines is being able to keep them on the road. All the components are extremely well made, but the complexity of the whole is pretty daunting. The air suspension, the mechanical fuel injection, certain weaknesses in the V8 (which can all be addressed, given enough time and money), the numerous electric and hydraulic peripherals and the ever-present threat of the tin worm all demand attention. It’s not easy to keep on top of everything, but I’m sure its highly rewarding. And since it’s a Benz, all the parts one might need are still available from the factory… for a price.

The W108/109 is probably the best-looking Benz ever made. This M100-powered variant is undoubtedly the fastest and most luxurious of the breed, so it’s a serious contender, at least in my book, to being the best Mercedes saloon ever made. They did try to recreate this superlative machine several times, such as with the 450SEL 6.9 or the Porsche-built W124 500E, but as far as I’m concerned, the original will always be unsurpassed.


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Vintage R&T Road Test: 1969 Mercedes 300SEL 6.3 – “Merely The Greatest Sedan In The World”, by PN