Buyers Guide - 1951-1962 W186/W189 300s

Richard Simonds

Web20300%20SedanCutout.jpgA brief buyers guide to the 300, 300b, 300c, and 300d series - Traditional Elegance of the1951-1962 Adenauers


1951-1962 300 sedans, coupes, cabriolets, and roadsters

At the conclusion of World War II, Germany was in shambles and the new Daimler management yearned for the glory years of the 1930s, when Mercedes-Benz vehicles were at the forefront of elegance and engineering.  Within a few years, the company had built enough of the basic 170 utility vehicles and small sedans to have some reserves that would allow them to build a line of higher-quality sedans and reclaim their position as a world leader in elegance.



In 1951, Daimler-Benz introduced the 300 Series four-door sedans at the Frankfurt Auto Show, followed soon after by the 300 Series four-door cabriolets. These cars had a body style reminiscent of the pre-war models: tall grilles and the voluptuous curves that were typical of the late 1930s and early 1940s. They offered a 6-cylinder engine with an overhead cam, dual carburetors, a 4-speed column-shifted manual transmission, a load-leveling mechanism on the back axle, a massive X-frame, a 12-volt electrical system, a central lubrication system for the front suspension, and interiors rich with wood, Wilton wool carpets, high-quality fabric or leather upholstery, and a general feeling of elegance.

The sedans actually cost more than the famed 300SL coupes and roadsters and the 300S and 300Sc coupes, cabriolets, and roadsters when new. As is typical, however, in the classic market, the sportier 300SL, 300S, and 300Sc models now command eight to 15 times more than the four-door sedans and three to five times more than the four-door cabriolets.

Given the styling and engine choices available in the United States, Mercedes-Benz had to make changes to its top-of-the-line models. Just think: You could buy a Cadillac or a Lincoln with a V-8 engine, an automatic transmission, and a low, wide body style for half the price of the top-of-the-line Mercedes-Benz sedan. Of course, the cabriolet models were available from Mercedes-Benz, but somehow that wasn’t enough incentive to sustain sales across the line. Still, the 300s were often purchased by wealthy people who did not want the ostentation that came with a Rolls-Royce, a Cadillac, or a Lincoln. The 300s offered traditional elegance that appealed to many buyers.

If these are the 300 Series, why are they called “Adenauers”? Because the chancellor of Germany – Konrad Adenauer – chose the 300 sedans as his official state vehicles. He liked them because they were elegant and well-engineered, and they were tall enough that he could wear his top hat while seated. He had several of them during his reign as chancellor and never lost his appreciation for what they represented at state functions.

The 300 sedans were mother to one of Mercedes-Benz’s most famous models, the racing Gullwings that earned Mercedes additional recognition in motorsports. The 2996cc engine block from the sedans was modified to cant at a 50-degree angle to fit in the low, space-frame body of the 300SL. The transmission, suspension pieces, and many interior components were lifted straight from the parts bins for the 300 Series sedans.

There were other derivatives of the 300 Series sedans and cabriolets, including the 300S and 300Sc coupes, convertibles, and roadsters. These two-door models were hand-built in very limited numbers. A total of 560 units of the 300S were built from 1951 to 1955. The 300Sc offered the fuel-injected engine of the 300d sedans as well as a number of other improvements that have made them nearly as desirable in the collector car market as 300SLs. There were just 200 of the 300Sc models built from 1955 to 1958.


Reasons to Buy an Adenauer

  • Pre-war elegance, luxury and styling ideal for grand touring and getting thumbs-ups when cruising.
  • Exclusiveness that means you will be noticed – particularly in the four-door cabriolet.
  • Excellent durability with many design features unusual for their time, such as front lubrication system, rear load-leveling mechanism, 4-wheel independent suspension, and 12-volt electrical system.
  • Room for six (with three in front), or room for five in luxury. It makes a  perfect wedding car.
  • Sometimes previously owned by important people, giving bragging rights and often increasing value.


Reasons Not to Buy an Adenauer

  • Restoration can be very expensive, well above the market value of the cars. It can become  a money-pit if not well-maintained.
  • Body trim parts are difficult, if not impossible, to find.
  • Rust in the body box frame of the body-on-frame construction and around headlights, door drains, and door sills.
  • Very leisurely performance – even for the 1950s.
  • Borg-Warner 3-speed automatic transmission is not a match for the torque of the engine and is expensive to repair, but can be replaced by a modern transmission.
  • Mechanics who understand these cars are becoming harder to find.



When considering one of these cars, remember that they are 50-60 years old, were hand-built, and were produced in limited numbers (only 10,723 sedans and 707 cabriolets built from 1951 to 1962). More than most models, if you are intent on owning an Adenauer, you must buy the best example you can afford. Before buying, think through your end objective for owning one. Restoration can exceed market value many times over, so decide if you are pursuing a labor of love or an investment.

  • With small numbers produced, and  limited interchangeability of parts, the car should be as complete as possible.
  • Carburetors are prone to warping and internal corrosion.
  • Electrical systems on “original” cars likely will need replacement wiring and some relays and switches.
  • Interior parts can be very expensive and difficult to find.
  • Original tube-type radios (e.g., Becker Nürburg) are very expensive to replace but can be rebuilt for a fee.
  • Suspension pieces are not readily available and are expensive to replace or rebuild.


Buying Tips

The 300, 300b, and 300c have the most classic, pre-war styling. The 300s (1951-early 1954) had no power brakes and only a 4-speed manual transmission, which was usually column-shifted.  The 300b added mildly assisted power brakes, vent windows, and dual-venturi carburetors for more horsepower. The 300c added a larger rear window, larger tires, and the option of an automatic transmission. A longer-wheelbase option was also offered with the 300c. The 300d is the most desirable engine and chassis (more power, fuel injection, longer wheelbase, optional divider window between the front and back seats), but it is, in my opinion, compromised by the Borg-Warner 3-speed automatic transmission. When adjusted properly, the transmission works fine, but acceleration is about on par with a locomotive. The 300d did offer other power-assist features such as power steering. All earlier models had “arm-strong” steering systems.


Nov. 1951300 sedan, 4-speed transmissions (most were column-shift), two single-barrel carburetors, rear load levelers, front suspension lubricationsystem operated by driver, low-compression engines to handle poor fuels.
March 1952300 cabriolet adds full open-top motoring to 300 sedan.
Feb. 1954300 sedan and cabriolet production end
March 1954300b sedan introduced with higher compression engines, double-barrel carburetors, brake booster, front-door vent windows, rear-door wind deflectors.
July 1955300b cabriolet production ends.
Aug. 1955300b sedan production ends.
Sept. 1955300c sedan adds larger back window, available Borg-Warner 3-speed automatic transmission, larger tires.
Dec. 1955 300c cabriolet adds full open-top motoring to 300c sedan.
June 1956300c sedan and cabriolet production end.
Nov. 1957300d sedan a redesign of body with 4-inch-longer wheelbase, pillarless hardtop construction, larger trunk and more squared-off fenders, fuel injection, higher-compression-ratio engine, Borg-Warner 3-speed automatic transmission.
Feb. 1962300d cabriolet production ends.
March 1962300d sedan production ends.

Note: Most 300c and virtually all 300d models had automatic transmissions in the United States. All post-war Mercedes-Benz engines can be operated with non-leaded gasoline because they have hardened valve seats and valves. The 300, 300b, and 300c can be operated on regular grade. The 300d requires mid-grade or premium because of its higher compression ratio and fuel injection.



Body parts: Buy wisely. Because they were hand-built, owning a complete car will mean the difference between being able to restore it and having a source of parts for someone else.

Carburetors: Solex carburetors must be rebuilt – there are no new ones. If the carburetor core is in good condition, rebuild kits can put them right, though having a mechanic who has rebuilt carburetors and knows exactly how to do it and which of the jets is placed in which position helps a lot. Old accelerator pumps were leather, newer ones have alcohol-resistant plastics that don’t always seal well. Fine-tuning the carburetors and balancing both of them after installation is as much art as science.

Interior parts: Rubber mats in front, Wilton wool carpeting in back, and the likelihood of full seat rebuilding require special talent – or a good upholstery shop that knows how to do it and where to buy the parts.

Suspension: Lack of regular lubrication turns grease into “concrete” and requires rebuilding front components. Adjusting the rear-leveling mechanism to make it work is difficult and may require new solenoids. Replacing rubber bushings everywhere is a given.


Ask Someone Who Owns One

Five years ago I purchased a 1962 300d from Bill Bruenning, long-time MBCA member and owner of the car for 25 years. Bill has since passed on but he was a very dedicated owner who watched the mechanicals as closely as its appearance. The car is nearly all original with only 69,010 miles.  It has the original spare, all the tools, and owners manuals. Its options include a Webasto sunroof with a pull-down sunshield which also can flip up when the sunroof is open to act as a wind deflector, a Becker Mexico radio, and central lubrication.  The car runs beautifully, and the real pleasure is taking friends through the great Missouri country. In this car, the journey is more important than the destination.

Rodger Van Ness
St. Louis, Missouri

1962 300d Adenauer owned by Rodger Van Ness

Owning and driving an Adenauer evokes polar opposite feelings. When it is well sorted-out, running well, and looking good, it is one of the most enjoyable experiences a driver and passengers can have. On the other hand, having to regularly repair parts that had not been well maintained by the previous owner can be both expensive and frustrating. It never had to be towed, but on more than one occasion, I found myself limping home or to my mechanic to get yet another problem fixed.

Richard Simonds
San Francisco Bay Area



Production Numbers
300/300b  sedan1951-19556,214
300/300b  cabriolet1951-1955591
300c  sedan1955-19581,432
300c  cabriolet 1955-195651
300d  sedan1958-19623,077
300d  cabriolet1958-196265

 * Source: Sports Car Market Magazine


Value Estimates

300 sedan $7,000$24,500$35,000
300 cabriolet$25,100$87,850$125,500
300b sedan $8,000$22,000$30,000
300b cabriolet $26,300$92,050$131,500
300c sedan  $7,800$26,500$39,000
300c cabriolet$26,900$94,150$134,500
300d sedan$10,000$23,000$23,000
300d cabriolet$22,800$79,800$114,000

Low value is a driver with visible flaws. Medium value is a car that is well maintained or partially restored and could win an award in a local car show. High value is a car that is in top concours condition – equivalent to or better than a new car straight from the factory.

Note: Cars sold in Europe may easily bring 50-60 percent more than these value estimates.


Technical Specifications

Years1951-1954 1954-19551955-19561957-1962
Engine: Incline, cast-iron block, aluminum head OHC, 6 (2996cc),# 186# 186 II # 186 II# 189
Compression ratio6.4:17.4:17.5:18.55:1









Horsepower (DIN/SAE)115/125    125/136125/136160/175
Chassis: Oval tube, X-frame,
with separate body frame – steel
Chassis number186 II186 III186 IV189

1. 2.95:1

2. 2.13:1

3. 1.46:1

4. 1.00:1

1. 3.44:1

2. 2.30.1

3. 1.53:1

4. 1.00:1

1. 3.44:1

2. 2.30.1

3. 1.53:1

4. 1.00:1

1. 2.303:1

2. 1.435:1

3. 1.00:1


Rear-axle ratio4.44:14.67:14.67:14.67:1
Engine speed at 62 mph3300342034203420
Front suspension: A-arms, coil springs with central lubricationAllAllAllAll
Rear suspension: Swing-axle, coil springs, independent with load levelerAllAllAllAll
Wheels5 x 155.5 x 155.5 x 155.5 x 15
Tire size7.10 x 157.10 x 157.60 x 157.60 x 15


(Booster on 300b, c, d)


197 sq. in.


228 sq. in.


228 sq. in.


228 sq. in.

Turning circle41-43 ft.41-43 ft.41-43 ft. 42-44 ft.
Wheelbase120 in.

120 in.

124 in. opt.

120 in. 124 in.  
Track: Front/rear58.2/60.058.2/60.058.3/60.058.3/60.0
Length194.4 in.199.4 in.199.4 in.204.3 in.
Width72.4 in.72.4 in.72.4 in.73.2 in.
Height63.0 in.63.0 in.63.0 in.63.8 in.
Ground clearance7.3 in.7.3 in.7.3 in.7.3 in.
Fuel capacity19 gallons19 gallons19 gallons19 gallons

Weight: Sedan/cabriolet (lbs.)

Automatic tran. add 10 lbs.    



0-62 mph (Auto is 1 sec. more)

18 sec.17 sec.17 sec.17 sec.
Top speed (Auto is 3 mph less)99 mph101 mph99.5 mph105.6 mph
Fuel consumption (Auto is 1 mpg less) 14.2 mpg14.7 mpg14.7 mpg13.7 mpg



For More Information

Mercedes-Benz Production Models Book 1946-1995 W. Robert Nitske, Motorbooks International, ISBN: 0-87938-190-6.
Illustrated Buyer’s Guide Mercedes-Benz Frank Barrett, Motorbooks International, ISBN: 0-7603-0451-3.
Mercedes-Benz 300 1951-62 Walter Zeichner, Schiffer Publishing Ltd., ISBN: 3-922617-21-2.

300c cabriolet with the top up.

300c cabriolet with the top folded.