Buyers Guide The M100 Elite: Grand 600, 300SEL 6.3, and 450SEL 6.9

Stu Hamel


















The M-100 Elite
 From Head of State to Drag-Strip King – Your Choice

A brief buyers guide to the M-100 engine cars: Grand 600, 300SEL 6.3, and 450SEL 6.9

Article and Photography by Stu Hammel
The M-100s, universally known by their engine type, are among the rarest, most powerful, and most luxurious automobiles ever produced by Mercedes-Benz.
During their 18-year reign as Mercedes-Benz’s flagship sedans, fewer than 17,000 were produced. Their original ownership roster reads like a who’s who among dignitaries, celebrities, and motorsports professionals, but today they are a rare sight.
In the early 1960s, Mercedes-Benz set out to create the most luxurious and technologically advanced luxury automobile available anywhere in the world. The result of the efforts of such iconic automotive designers and engineers as Paul Bracq, Rudolf Uhlenhaut, Erich Waxenberger, Kurt Oblander, and others was the Grand 600 sedan. This was a car larger in scale than any others produced in recent history; was replete with a devastatingly powerful 6.3-liter V-8 M-100 engine; required the driver and occupants to expend little effort to operate all comfort conveniences; and could be custom tailored to meet any special requirements an owner might desire.

Several years after the introduction of the Grand 600, young engineer Waxenberger, a racing enthusiast, experimented with the M-100 engine by installing it in the smaller and lighter W109 body sedan. In 1968, after numerous race-course trials and convincing arguments to Mercedes-Benz management, this became the 300SEL 6.3 sedan, known as the fastest production sedan available. Numerous automotive writers at the time aptly used the term “Banker’s Hot Rod” to reference the new model. Subsequent to the 300SEL 6.3, a variation of the M-100 engine was placed in the new, more modern W116 chassis, becoming the famous 450SEL6.9. The M-100 models began production in 1964 and continued through 1981.
The Grand 600s, available as a five-passenger short-wheelbase sedan, a seven-passenger long-wheelbase sedan (Pullman), and two varieties of Landaulets, were introduced to the market with features including air suspension and a full Comforthydraulic system responsible for operating windows, seats, sunroof, climate control, braking, and trunk opening and closing. The air suspension produced a ride second to none, while the hydraulic amenities provided silent operation of power functions, because no electrical motors were required. There are essentially two generations of 600 cars: 1964-1968 and 1969-1981 (to 1972 in the U.S.).
In gross generalities, the first-generation 600 cars are more elegant, and the second-generation cars are more reliable. The first-generation cars have more wood inside, specifically under each door armrest and covering the instrument pod. The side mirrors are smaller, and the air-conditioning system boasts front and rear components. The later cars abandoned this complex system in favor of a second “booster” fan for the rear a/c outlets. Finally, the hydraulic-assist door-closing system on the first-generation cars was abandoned in 1969 for reliability reasons. All Grand 600s shared the same mechanically fuel-injected 6.3-liter V-8 engine and automatic gearbox. There were some minor mechanical differences in later years as well.
The 300SEL6.3 sedans underwent subtle modifications during the production run from 1968 to 1972. Early cars were a bit more powerful, with a 9:1 compression ratio. This was modified to an 8:1 ratio in U.S. delivery cars shortly after they were first introduced in this country. Other than minor modifications in turn-signal-lamp shape and some interior improvements, all 6.3s were relatively similar. The same is true for the 450SEL6.9. European-delivery 6.3s and 6.9s had better headlights, and in the case of the 6.9, a manual climate-control system, though the Chrysler-based system found in U.S. cars was also available in later years in non-U.S. cars. European 6.9s had the preferable stacked bumpers as opposed to the U.S. battering-ram

Reasons to Buy an M-100 Vehicle

  • Current and future collectibility (values are rising and should continue).
  • Great niche appeal: 600 for the luxury classic buyer, 6.3 for the classic sport sedan type, and 6.9 for the early Q-ship fanatic.
  • All three types are unique in their way and have great classic appeal – you will be noticed upon arrival.
  • A reasonable supply of these cars comes to market, and entry costs are not astronomical for what you get.
  • Most parts are readily available.
  • DIY maintenance can be accomplished with time and patience.


Reasons Not to Buy an M-100 Vehicle

  • Poorly maintained examples should be avoided at all costs – refurbishment costs are more than you want to consider.
  • Skilled service technicians are not abundant.
  • Parts are more expensive than average – in some cases, way more.
  • Other than the landaus, these are not convertibles, so remember that you are buying a sedan.
  • 600 Comforthydraulic system is prone to leaks and failure.
  • Catastrophic failure of suspension system will leave you stranded.



  • Brake hoses and caliper condition, because lack of use normally results in restriction of fluid and the death of the caliper function.
  • Leaking Comforthydraulic components in the 600. Check door bottoms; under dash, trunk, and hydraulic fittings in the engine compartment; and under the vehicle.
  • Undercarriage damage due to flattening of suspension. Potential damage to fuel tank, exhaust, and structural components.
  • A/C evaporator drain hose into the interior of the car can clog, causing rust in the floor and mildewed carpets.
  • Rust in quarter panels and door sills.
  • Misaligned 600 trunk lid from improper closing of lid. Ruins the aluminum lid.
  • Operability of all window, seat, climate-control, and sunroof switches.
  • Integrity of wooden pieces. Replacement and refurbishment is expensive.
  • Upholstery. Original leather is no longer available. Some replacement velour is now available. Original upholstery with patina is preferred. A new interior will be expensive!
  • Service records, service records, and more service records. You will come to hate a neglected M-100.
  • Air suspension on 600 and 6.3, hydropneumatic on 6.9. Test the suspension to make sure it operates through all ranges.   If the engine is cold and the car is standing properly, the suspension is likely to be in decent shape.
  • Paint. Check paint integrity. A proper respray on a Grand 600 can cost more than $20,000.


A Real-World Example
In our travels across the U.S. last winter in a 450SEL 6.9 that my wife Twila and I had purchased in Los Angeles, we made a stop to visit friends and fellow International M-100 Group members in Santa Fe, New Mexico. What a treat to see one of the best examples of a Grand 600 SWB car that I have had the pleasure of experiencing. This example, which is currently on the market, is a 1969 model unique in several respects. Most notably, this is a car with a divider that was originally delivered to its first owner, a captain of industry in the Middle East. It is one of just a few 600s to be ordered with a full-body undershield. It is a vehicle with original documented mileage of approximately 16,200 miles since new.

Other than the uniqueness of the car’s history and its special equipment, this is a prime example of what to look for when beginning a search for a 600. It meets every definition of a well-maintained 600. Although the car has low mileage, it is still critical that it has been not only properly serviced, but also put on a preventive schedule to avoid the pitfalls of permitting perishable items from deteriorating from nothing more than time and environmental conditions.
I inspected the car carefully during our visit, which turned out to be the highlight of our trip. Cosmetically, the car was absolutely stunning, which was evident by the successes the owners have had in numerous concours events around the country. The paint was absolutely flawless, and the woodwork was in perfect original condition, as were the magnificent Cognac leather upholstery and trim. The original Feintuftvelour carpeting appeared never to have been stepped on. This was quite simply what a Grand 600 looked like coming off the production line.

Mechanically, the car is as pristine as it is cosmetically. I tested every single function and can report there were no problems noted. I searched carefully for any signs of hydraulic leaks and could find none. This is rare, even in the best-maintained 600s. Due to the owner’s attentiveness and desire to have a car that he could drive anywhere at any time if he so chose, I could find no system in need of attention. This is what preventive maintenance can do for you. Do not expect to easily find a 600 that needs no work of any kind to be driven as intended. This car is clearly the exception. I must also say that due to its provenance and condition, it does not fall neatly into the parameters of the pricing data in this Buyers Guide.
As a parenthetical note, Twila and I drove our 1979 6.9 from Los Angeles to Reading, Pennsylvania, with no issues whatsoever. Again, based on its maintenance history, we were not terribly worried about driving a car with 175,000 miles on it across the country.

The International M-100 Group

I would like to thank the editorial staff of The Star for the opportunity to contribute to this publication. I currently serve as president of the International M-100 Group, a Daimler officially recognized Mercedes-Benz Club. The International M-100 Group is dedicated to the preservation and promotion of M-100 vehicles. We have an outstanding website with technical information and a web forum, in addition to producing a quarterly publication known as the Lode Star. Membership is worldwide, and we convene annually at different locations to “play car.” Our web address is                  
Stu Hammel

1963First three Grand 600s produced
1964Beginning of worldwide sales of Grand 600
1966Erich Waxenberger begins experimentation, installing M-100 engine in W109 chassis automobile
1968300SEL 6.3 goes into production with worldwide sales beginning the same year
1969Changes to the 600: less wood, elimination of hydraulic door-closing assists, revised a/c system. 6.3 gets redesigned dash, turn signals, and shift pattern
1972End of U.S. sales of 600 models due to emissions requirements and economy. End of 6.3 production
1975Beginning of sales of 450SEL 6.9
1980End of production of 450SEL 6.9
1981End of production of Grand 600


Value Estimates

600 Grand 1963-1966$24,885$95,115$160,000
600 Grand 1967-1969$32,900$106,700$170,000
600 Grand 1970-1972$44,070$121,620$180,000
600 Pullman 1963-1972$48,200$146,580$225,000
600 Pullman 1973-1981Insufficient data to estimate values
300SEL 6.3 1967-1969$7,320$33,000$65,000
300SEL 6.3 1970-1972$8,500$36,000$70,000
450SEL 6.9 1975-1978$5,500$25,350$55,000
450SEL 6.9 1979-1980$6,000$29,000$65,000
(add 5 percent for ABS brakes)
  • 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. (source: John Olson)



Grand 600

     Short Wheelbase



Pullman (6-door)




300SEL 6.36,526
450SEL 6.97,380


Technical Specifications

Model600 and 6.36.9


Bosch mechanical

fuel injection

2 single overhead cams

5 main bearings


CIS electronic

fuel injection

2 single overhead cams

5 main bearings

Bore x stroke (in/mm) 4.06 x .74 / 103 x 954.21 x 3.74 / 107 x 95
Displacement (
386.26 / 6,329417.1 / 6834
Horsepower300 @ 4,100250 @ 4,000
Torque (lb.ft. @ rpm)434 @ 3,000350 @ 2,500
Maximum engine speed4,800 rpm5,300 rpm
Compression ratio

9:1 (’63-’72)

8:1 (after '72)

8:8:1 (Europe)

8:1 (U.S. '75-'81)


3-speed auto

with torque converter

3-speed auto

with torque converter