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Mercedes-Benz C111

Overview

Mercedes-Benz built sixteen C111s over ten years, painted them a shade of orange named after a rosé wine, and refused every offer for all of them.

The first car appeared at Frankfurt in 1969 with a three-rotor Wankel behind the seats, a fibreglass body on a steel platform, gullwing doors, leather and air conditioning. It was not a styling exercise. Daimler-Benz was seriously evaluating the rotary engine, and the C111 existed to find out what it did in a car rather than on a test bed. A four-rotor version followed at Geneva in 1970 with 260kW and a reported 300km/h.

Then the answer came back negative. The Wankel used around half as much fuel again as a piston engine of the same output and could not meet the emissions rules coming out of California, and after the 1973 oil crisis Mercedes closed rotary development down at the start of 1976.

What happened next is the interesting part. The same shell came back with a five-cylinder turbodiesel in it, then a slipperier version of the same idea, and finally a twin-turbo V8. Between 1976 and 1979 those cars took world records at Nardò that permanently changed what a diesel engine was assumed to be.

Distinctions

The defining attributes and collector status that make this car garage-worthy.

Poster Car

The car on the bedroom wall, the one people dreamed about before they could drive.

Octane Files Select

Renowned for its history, engineering, or cultural weight.

Collectibility scorecard

Rated 1 to 10 on the traits that matter for owning, driving, and holding on to a car like this.

Desirability

8/10

Rarity

10/10

Driving thrill

8/10

Investment trajectory

2/10

Usability

2/10

Ease of restoration

2/10

Cultural impact

7/10

Electronic dependence

Fully analogHeavily electronic

Nothing in the C111 computes. Both Wankels ran mechanical Bosch direct injection and the diesels a Bosch PE inline pump feeding at up to 40MPa, so in every version the fuelling is decided by cams and levers. Throttle, clutch and the dogleg five-speed are cables and rods. It sits at 2 rather than 1 only because this was never a stripped prototype: it left the works with a full road-car electrical system, leather, air conditioning and a Becker cassette radio mounted vertically in the console, and the record cars carried instrumentation ordinary cars of the period did not.

Market data

Demand tier, price trend, and typical values by condition. Our own assessment, not a quoted valuation.

Demand tier

EntrySolidHighBlue-chip

The proven elite. Values are established, liquid, and defended at every auction.

Value trajectory

AppreciatingStableCooling

Values are holding steady. What you pay today is what it's worth tomorrow.

Price by condition

Driver

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Excellent

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Concours

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No C111 has ever been sold and there is no price to report. All sixteen cars remain the property of Mercedes-Benz, which has kept them since they were built and still shows them. Collectors are widely reported to have sent blank cheques after the car's Frankfurt debut in 1969, and Mercedes' own retrospectives repeat the story. Whether the cheques were literal or not, no offer was ever taken. The tier here describes standing rather than liquidity: this is a blue-chip object with no market at all, which is a different thing from an expensive car. Mercedes has never put a figure on one, even after selling a 300 SLR in 2022 and proving it is willing to sell from its own collection when it wants to.

Buyer's guide

What anyone seriously considering this car should know first.

Why it's worth it

The research car that made the turbodiesel fast, and was never sold to anybody

Callout

A diesel Mercedes averaged around 252km/h for sixty hours at Nardò in 1976

What to watch for

Nothing to buy, so this is a guide to telling the four cars apart, which matters because they get conflated constantly. The C111-I of 1969 is the short, blunt one: three-rotor Wankel, 3,600cc, 205kW, shown at the Frankfurt IAA. The C111-II of 1970 is the shape most people picture, cleaner at the nose, with the four-rotor 4,800cc engine at 260kW. Thirteen of the sixteen cars come from these two phases. The C111-IID of 1976 looks like a tidied II and has the five-cylinder turbodiesel in it. The C111-III of 1978 does not look like the earlier cars at all: longer, smoother, wheels covered, drag coefficient down to 0.195. Two diesel cars were built. The C111-IV of 1979 is the silver one, single-seat, twin-turbocharged V8, and the only one of its kind. If you are ever offered one, it is a replica or a misunderstanding. Note also that the build count is contested: Wikipedia itemises sixteen across the whole programme, while other reputable accounts say six or a dozen, both of which appear to be counting only the orange Wankel cars they were writing about.

The Story

Driving character

Almost nobody has driven a C111, and the few accounts that exist agree on the same things. The four-rotor Wankel is the party piece. It makes its power with none of the pulses a piston engine gives you, described by one tester as latex-smooth, and it revs with an eagerness that flatters everything around it. It also drinks oil and consumables at the rate that eventually killed the programme. The rest is more ordinary than the shape suggests. The ZF five-speed is a dogleg with a push-button detent on the knob to reach first, precise in the hand and a little loose in its action. The steering is heavy. The view out is strange: arching front wings that seem a long way apart, and mirrors that mostly show you your own bodywork. Inside it is a 1970 Mercedes rather than a racing car. Wide vinyl-lined sills, a big steering wheel, a Becker cassette player standing vertically in the console, leather, air conditioning. Even the gullwing doors are practical rather than nostalgic: the sills are deep, and conventional doors would not clear them.

Design

Bruno Sacco drew it, years before he ran Mercedes design, and it is the least Mercedes-looking object the company has ever put on wheels. The C111 is a wedge from a decade of wedges, but it is a wedge with a Mercedes' worth of detail in it: gullwing doors with fixed windows and small swivelling panels acting as air extractors, a fibreglass shell over a steel platform, and a cabin trimmed as though somebody might commute in it. The colour does as much work as the shape. Mercedes calls it Weissherbst, after the rosé wine, and it is the reason a car that never went on sale is remembered by people who were nine years old in 1970. Orange was not what Stuttgart did. The later cars went the other way entirely. The C111-III of 1978 gave up everything to airflow, with covered wheels, a longer tail and that 0.195 drag coefficient; the C111-IV of 1979 arrived in silver, single-seat and severe. Ten years took the same project from a show car with air conditioning to something that looked like it belonged on a salt flat.

Motorsport pedigree

The C111 never raced, and that is not an oversight. Mercedes had walked away from motorsport in 1955 and did not return in any serious way until the mid-1980s, so a competition programme for a Wankel prototype was never on the table, whatever the gullwing doors suggested. What it did instead was chase records, which in the 1970s was a manufacturer's other way of proving something in public. Nardò, June 1976: the C111-IID ran for sixty hours and took sixteen world records, thirteen of them diesel marks and three absolute, at an average of around 252km/h. The drivers were the company's own engineers, Hans Liebold, Guido Moch, Erich Waxenberger and Joachim Kaden, not hired stars. Nardò, 30 April 1978: the C111-III took nine outright world records in twelve hours, six of them distance marks from 100km to 1,000 miles and three of them time marks at one, six and twelve hours. Nardò, 1979: the C111-IV lapped at 403.78km/h with Liebold driving, a closed-circuit figure that stood as a benchmark for years afterwards. Three visits to the same Italian bowl, and the reputation of an entire fuel permanently altered.

In culture

For a car nobody could buy, the C111 got about. Mercedes' own retrospectives describe the orange wedge as something a whole generation remembers from toy cars, from Quartett card games and from posters, which is exactly right: Dinky modelled it as number 224, and Matchbox sold a Speed Kings version between 1973 and 1975. Plenty of people who could not name another Mercedes could draw this one. It also has a strange afterlife in the story of the supercar. The C111's thinking fed into the CW311, which Mercedes did not build but which became the Isdera Imperator, and into the C112 of 1991, which took 700 deposits before Mercedes cancelled that too. The company kept designing mid-engined cars it had no intention of selling. And it kept the C111s. All sixteen remain in Stuttgart's hands, brought out and run at the company's own events, which for a research programme that never earned a penny is its own kind of statement about what Mercedes thought it had built.

Rivals

Cars from other manufacturers that competed for the same buyers when new.

BMW M1

Germany·Exotic·1978–1981

Ferrari 512 BB

We haven’t profiled this car yet. Request to add

Lamborghini Countach

Italy·Exotic·1974–1990

Maserati Bora

Italy·Sports·1971–1978

Owning One

Why collectors want it

You cannot own one, and in fifty years Mercedes has given no sign that this will change. All sixteen are company property. None has been sold and none has been offered.

That makes the C111 an unusual entry in a collector-car catalogue, and it is here because the argument does not depend on a transaction. It is the most complete surviving record of a manufacturer thinking out loud: four different engine families in one body, tried in public, over a decade, with the results published either way.

For an enthusiast the value sits in the negative result as much as in the records. Mercedes spent years on the Wankel, built a car good enough to make people wave chequebooks at it, established that the engine could not meet the fuel and emissions standards that were coming, and said so. Then it used the same car to prove the opposite case for the diesel, and put a turbodiesel round an Italian test bowl at speeds nobody associated with the fuel.

The 300 SLR earns its place by what it won. The C111 earns its by what it settled.

Which one to look for

If the programme has a headline car it is the C111-III of 1978, and almost nobody names it. The two Wankel cars are the famous ones and they own the image: orange, gullwinged, thirteen of the sixteen built, and the reason the C111 was ever on a bedroom wall. The 1970 four-rotor is the better of the two, with 260kW and a reported 300km/h. But the III is where the programme delivered. It is the same idea taken seriously: a 0.195 drag coefficient, covered wheels, a three-litre five-cylinder turbodiesel at 170kW, and nine outright world records in twelve hours at Nardò on 30 April 1978, including the one-, six- and twelve-hour marks and distances from 100km to 1,000 miles. Top speed 338km/h. Fuel consumption of 16 litres per 100km while averaging 325km/h. The C111-IID of 1976 got there first with sixteen records in sixty hours. The C111-IV of 1979 went fastest of all, 403.78km/h round Nardò with Hans Liebold driving, but by then it was a silver single-seat missile sharing little with the orange car beyond a project name.

C111-I · 1969

The first car, shown at the Frankfurt IAA in September 1969. Three-rotor M 950 F Wankel of 3,600cc producing 205kW at 7,000rpm, mounted behind the seats in a fibreglass body over a steel platform chassis, with gullwing doors, leather trim and air conditioning. Short and blunt-nosed compared with what followed.

C111-II · 1970

Shown at the Geneva Motor Show in 1970 and the shape most people picture. Four-rotor M 950/4 Wankel of 4,800cc producing 260kW at 6,000rpm, with a cleaner nose and a reported 300km/h. Mercedes ended Wankel development at the start of 1976 on fuel consumption and emissions, and this is the car the decision was made on.

C111-IID and C111-III · 1976–1978

The diesel record cars. The IID used the OM 617 five-cylinder turbodiesel of 3,005cc at 140kW, with a wastegate-less turbo and an intercooler, and took 16 world records at Nardò over 60 hours in June 1976. The III of 1978 rebodied the same idea for airflow, reaching a 0.195 drag coefficient and 170kW, and took nine outright world records in twelve hours on 30 April 1978, with a 338km/h top speed.

C111-IV · 1979

The last car and the fastest. Single-seat, silver rather than orange, powered by a 4,500cc M 117 V8 with twin KKK turbochargers producing 368kW at 6,000rpm. Lapped the Nardò bowl at 403.78km/h with Hans Liebold driving, a closed-circuit benchmark that stood for years.

What owning one is like

Nobody has ever had to live with a C111, and the reasons are worth spelling out, because they are the same reasons it was never sold. The four-rotor Wankel was fast and smooth and it consumed its own apex seals, drank oil as a matter of design, and used around half as much fuel again as a piston engine making the same power. That is a research problem in 1970 and an ownership problem in perpetuity, since nobody has made a part for a Mercedes rotary since development stopped at the start of 1976. The diesel cars are the opposite. An OM 617 five-cylinder is one of the toughest engines Stuttgart ever built, and the turbocharging and intercooling were done properly rather than hopefully. Those are the C111s that could be run today with the least drama, which is presumably why they are the ones that come out most often. Everything else is a fibreglass shell on a steel platform, both repairable, over suspension geometry that later reached production. The hard part was never the car. It was the question the car was built to answer.

Upkeep & parts

There is exactly one workshop in the world for this car, and it belongs to the company that built it.

Mercedes-Benz Classic keeps the C111s running, which for the Wankel cars means keeping alive parts for an engine family that was cancelled at the start of 1976 and never sold to anyone. Rotor housings, apex seals and the mechanical injection for a three- or four-rotor M 950 are not reproduced by anybody; what exists is what was made at the time.

The diesel cars are easier in a way that is almost funny. The OM 617 five-cylinder is the engine from the W123 and the 300 SD, one of the most widely produced diesels of its era, so the block, the crank and most of the internals are the least exotic components in the entire programme.

For a reader the useful resource is an archive rather than a parts supplier. Mercedes' public archive publishes the technical records for these cars, and the documentation around the record runs is more accessible than for almost any other prototype of the period.