’70s super saloon showdown: Mercedes-Benz 300 SEL vs. Jaguar XJ12

It was a battle royale: HMS Hood versus the Bismarck. Twelve cannons versus eight on the deck. Early on in the ’70s, the Jaguar XJ12 and the Mercedes-Benz 300 SEL 6.3 fought for buyers in the equivalent of a sumo wrestling match performed in three-piece suits.

Back in WWI, Britain devised a class of submarine hunters using heavily armed ships disguised as merchant vessels. Designated as Q-ships, they cloaked their big guns so they could lure the subs into making surface attacks, at which point they’d simply open fire and sink them.

Automotive Q-ships–fast sedans that don’t broadcast their performance potential to the world–can be found in a wide range of models and years. The concept of factory sleepers emerged in the late 1950s; some call the Hemi-powered 1957 Chrysler 300C and the 1959 Jaguar Mark 2 two of the first from the “wolf in sheep’s clothing” brigade.

The Mercedes-Benz 300 SEL 6.3 has long reigned at the top of the segment, but back in the day, its big V8 was challenged for position by the purring 12 cylinders of a contemporary: the Jaguar XJ12.

Decades after these genre-defining Q-ships debuted, enthusiasts have reveled in anonymous “hammers” like the Audi S8, BMW 760i and various S-class Benzes. Today, assuming you have nearly a quarter-million, Mercedes will even sell you a V12-powered, full-size sedan that delivers 621 horsepower along with more than 700 lb.-ft. of torque.

Still, the classic Benz and the Jag remain gold standards for their ilk. Although “overpowered” is the word that defines them both, in reality, they could not be more different in character. The Mercedes-Benz reacts with the subtlety of a sledgehammer, the Jaguar is a suave steamroller. We spent a day with each of them to explore the way these two variations developed the theme.

Mercedes-Benz: A Hotrodder’s Delight

The Mercedes was the first to appear, landing in 1968 as the brainchild of Benz engineer and test driver Erich Waxenberger.

Waxenberger, who had a thing for V8s, had already experimented with the 6.3-liter V8 engine that powered the mighty 600 limousine used by kings and dictators alike. He had somehow found the space to put that engine in a 280 SL pagoda, but the plan never went any further. A follow-up idea quickly grew, however, after the editor-in-chief of Auto Motor und Sport made fun of the Mercedes development department during a visit to Stuttgart.

At the time, the glory days of the 300 SL were long gone, and the editor was merciless to Waxenberger and his then-chief, Rudolf Uhlenhaut. “So,” he queried, “you make cars for old geezers then?”

Waxenberger, not surprisingly, didn’t take the remarks too well, and started thinking about a comeback–but not a verbal one. At first he thought about turbocharging Mercedes’s 3-liter, six-cylinder engine, at the time the best thing the brand offered to the masses, but that proposal was met with resistance from the technical department. It was then that he realized he already had the answer: the V8 he’d been experimenting with. In the SL, the 6.3 liter was a very tight fit; but in the S-class, it would be somewhat less cramped.

Waxenberger kept the project under the radar. He borrowed a 250 SE Coupe along with a V8 engine. The work to marry them took place after hours and on holidays. On a Friday evening in 1967, the prototype was finally ready for a first run.

He took it out for a test along the factory offices at 10:30 in the evening. The next morning, he got a call. His boss, Rudolf Uhlenhaut, was on the line: Care to discuss that V8 driving past my office?

Waxenberger explained how he wanted to create an S-class that would leave sports cars for dead. Uhlenhaut’s reply was to the point: Can’t believe the engine fits, and I want to drive that car tomorrow.

Soon after, the entire board of directors sampled the swapped car. Just one person seemed displeased: The sales director, who worried that there would be few takers. In the end, Mercedes-Benz sold more than 6000 copies of its muscular sedan.

A minor exterior detail separates the V8-powered version from the standard 300 SEL models: the extra pair of fog lights and the double headlights at the front. Together they give the Paul Bracq design a more prominent face.

More noticeable was the extra power. Where the classic 3.0-liter six was good for 170 horsepower, the 6.3-liter V8 added another 80 horses to bring the total to 250.

Mercedes had an Autobahn rocket, and Porsche suddenly got complaints from 911 owners who couldn’t understand why they had just been passed by a stately Benz.

Even though the 300 SEL 6.3 weighs 3924 pounds, it hits 60 mph from a standstill in less than 6.5 seconds. Top speed is 136 mph. Even by today’s standards, that is impressive.

Jaguar XJ12: Big Power From the Beginning

The Jaguar XJ12 is a different kettle of fish. To begin with, it’s much prettier. The Mercedes looks impressive and dominant, but it makes no effort to please the eye. The XJ seems only to become more beautiful as the years go by.

The Series 1 headlights and its bonnet’s famous power lines give this XJ a much more graceful appeal over the Series 2 cars’ raised front bumper; on a Series 1 car like one, the lowered bumper displays a more impressive radiator grille. Purely on looks, the Mercedes doesn’t stand a chance.

Like the Benz, this one also has roots in 1968. That year Jaguar unveiled the XJ6, known during development as the “eXperimental Jaguar.” When it made its debut with Jaguar’s famous inline-six, it was named Car of the Year by Car Magazine.

But Jaguar had something bigger in mind for the XJ all along. In 1972, that vision was realized in the form of the XJ12. The V12 engine, which was conceived by Walter “Wally” Hassan for the doomed XJ13 project, would also reappear with just a single overhead cam per bank to power the E-type.

That same engine is what is found under the magnificent, forward-opening bonnet of the XJ12, and there is a lot of it. Where the Mercedes’s engine bay looked crowded with the V8, the Jaguar’s looks positively crammed as every last inch has been used to install the 5.3-liter V12. The three-speed BorgWarner automatic gearbox is pushed deep into the passenger compartment, where there is even less available space.

Less space does not mean less charm. Inside you’ll find a club environment that includes plush seats and fine leather. The tall transmission tunnel divides the car into two separate compartments; it’s more cozy where the Mercedes delivers a roomier feel.

The XJ12 comes from a time when Jaguar was in full transformation. William Lyons had left the company in 1972, and the British Leyland conglomerate saw a lot of social unrest in the factories. Less attention to detail was paid in the finishing of the cars. On top of that, the first oil crisis was just waiting around the corner. When you have a car like the Jaguar with two fuel tanks to fill, this was not good news.

Fastest Limousine on Earth

Each of these cars can claim advantages in the numbers game, depending on the yardstick used. The Jaguar takes the initial lead over the Mercedes–266 horsepower versus 250–but the Mercedes offers more torque: 434 lb.-ft. versus 332 lb.-ft.

Both cars weigh nearly 2 tons, but thanks to its slower transmission and one less available gear, the Jaguar is powerless in a straight-line duel. It takes nearly 8.4 seconds to hit 60 mph; the Benz is almost 2 seconds quicker to the mark.

“The legacy of these sleepers lives on in today’s AMG and XJR sedans. Yet somehow, the older ones are much better at playing the Q-ship game.”

Jaguar makes up for that deficit with a slightly higher top speed–140 mph versus 136 mph–allowing it to lay claim in 1972 to the title of fastest limousine on Earth.

The Jaguar shows even less appetite for the corners than the Mercedes, with steering that takes its time transferring orders from the bridge to the wheels. Its brakes also ask for more consideration. Yet, once it gets rolling, the Jag is every bit as mesmerizing as the Benz. Both still feel fast by modern standards.

The XJ12 came late in the career of the Series 1 XJ, so just 2474 short-wheelbase examples were sold before the Series 2 kicked in. The XJ12 turned out to be more popular later on, with a career that stretched all the way to 1992.

Running the Jaguar takes a bit more maintenance, though, as keeping that big V12 cool requires some regular attention. The Mercedes is easier in that respect.

So, how to pick a winner? The Jaguar’s price of entry is much lower, but from a performance point of view it has no chance. However, it also possesses that difficult-to-pinpoint element called charm. Remember what we said about it capturing the feel of a Rolls-Royce? After handing back the keys, we found ourselves thinking about the Jaguar much more than the Benz.

The legacy of these sleepers lives on in today’s AMG and XJR sedans. Yet somehow, the older ones are much better at playing the Q-ship game. It’s a bit like this: Although Mark Wahlberg gave it his best shot, when you need someone to play Charlie Croker in “The Italian Job,” no one will ever be better than Michael Caine.

Thank you, Albion Motorcars, for help in bringing together these cars.

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