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Auto Test

Mercedes-Benz 450SEL - 4,520 c.c

AutoCar, 4 May 1974

Winner of 1973 Car of the Year award, provides unrivalled quality and comfort, allied to high performance and excellent economy.

From this angle, little distinguishes 450SEL from other S-Class models. Shallow grille is supplemented by large air intake beneath bumper. Outboard-positioned foglamps are evident within light units.

ALTHOUGH CONSIDERABLY less expensive than the massive 600 models, the 450SEL has assumed the role of "flagship" of the Daimler-Benz range. Rightly so, for this luxurious model - winner of the 1973 Car of the Year award - represents the very pinnacle of passenger car development.

First seen at last year's Geneva Motor Show, the 450SEL is four inches longer than the other S-class versions. All of this extra length goes towards making additional room for back seat passengers. Although the model is built mostly in conventional saloon form, German customers (but not British ones) may specify at extra cost a division to turn the car into a formal limousine.

The power unit is Daimler-Benz 4.5-litre V8. As with the other models using this engine, the 450SEL has automatic transmission and power steering as standard. Anti-squat rear suspension is also part of the standard package.

It comes as no surprise to find the 450SEL exceedingly well equipped, but there are, none-the-less, some listed extras. The most important of these is full air-conditioning, while an electrically-operated sliding roof and light-alloy wheels are also extras. Surprisingly, an additional charge is also made for the built-in safety belts.

Despite extra length, car's appearance is nicely balanced. Drip-rails are carefully profiled to minimise wind noise and keep side windows clean. Body contours are designed to keep lamp clusters clean; latter feature built-in rearguard lamps.

Autocar was privileged to road test a left-hand-drive example of the 450SEL in Germany, before it was generally available in Britain. All comments in the body of the report refer to this particular car, though we conclude with some observations relevant to the right-hand-drive example borrowed in Britain for photographic purposes.


A shot of the left-hand-drive car taken in its native Bavaria.

Although Daimler-Benz' claim of 225 bhp (DIN) is likely to be be a very honest one, the cars top speed of 134 mph reflects considerable credit on aerodynamic efficiency of the somewhat massive-looking body. Our best one-way figure, achieved in near perfect conditions, was no less than 136 mph. At this speed, the tachometer needle nudges 5,700 rpm - just 100 rpm below the edge of the red sector.

Despite the careful attention paid to passenger protection, the cars kerb weight of 34.9cwt is comparable with that of others in its class. Even so, acceleration is good, rather than spectacular. A slightly lethargic step-off results in the mediocre 0-30 mph time of 3.7 sec; With the transmission left to its own devices, 60 mph comes up in 9.5 sec and 100 mph in 25.5 sec, the gear changes taking place at 4,800 and 5,400 rpm respectively. Delaying the changes to 5,800 rpm by using the manual selector improves these times to 9.1 and 24.4 sec.

This kind of performance is entirely satisfactory for a car of this type. Nevertheless, the model is rather, except for maximum speed, than the 280SE 3.5 tested in Autocar almost two years ago (1 June 1972). Although the earlier car achieved only 128 mph, it reached 60 and 100 mph from a stand-still in 8.4 and 23.7 sec respectively - this with a 25 bhp (DIN) disadvantage in terms of peak power. There are two reasons for this. First, the 450SEL weighs nearly 4cwt more; second, its automatic transmission has three mechanical ratios and a torque-convertor rather than four ratios and simple fluid coupling of the earlier design. By way of compensation, the newer transmission is very much smoother, while another advantage is the decrease in fuss resulting from the lower engine revs at traffic speeds.

Our fuel flowmeter equipment is not compatible with high-pressure fuel injection systems of the type used by Mercedes. This is a pity, for the 450SEL's overall fuel consumption of 14.7 mpg is quite remarkable for a car of this weight and power. Even better results (nearly 15.0 mpg) were achieved over part of the test distance, though this was offset by the 13.9 mpg recorded during a spell which included performance testing and a good deal of very high-speed autobahn driving.

With a tank capacity of 21 gallons, the car's worry free range is likely to exceed 250 miles. The handbook advises the use of fuel with an octane number not less than 98RM; from the British viewpoint this is unfortunate in that the minimum British standard requirement for four-star petrol is 97RM. Care should therefore be taken in selecting such fuel, not all brands of which have a sufficiently high anti-knock value. In the data table, we give the fuel requirement as super-premium because of this doubt.

Oil consumption is very low, being of the order of 1,900 miles per pint. Changes are called for at 5,000 mile intervals, with the result that topping-up should rarely be necessary in between.

Engine and transmission

Underbonnet accessibility is better than crowded appearances suggest.

Surprisingly compact, the engine has a cast iron block and exhaust manifolds, and light-alloy cylinder heads, sump, convertor housing and front cover. The bore diameter, at 92mm, is the same as that of the basically similar 3.5-litre engine, but the stroke has been increased from 65.8 to 85mm. Because of the higher inertia loads which result, the maximum permitted speed is reduced to 5,800 rpm from the 6,300 rpm of the smaller engine; this limit is backed up by a centrifugal-type ignition cut-out. This was found to operate precisely as intended, cutting the engine just as the needle touched the red.

Some of the engine's apparent compactness is owed to the way the Bosch electronic fuel injection system nestles unobtrusively between the cylinder banks. The system's behaviour is impeccable, irrespective of engine temperature. There is never any suspicion that mixture strength is anything but exactly right for the prevailing conditions.

Although the engine is mechanically quite noisy, very little of this can be heard inside the car. Even when working hard, the unit feels smooth and remarkably unobtrusive. All that can be heard is a muted growl, possibly emanating from the induction system.

Thanks to the use of a viscous coupling, one is never conscious of any noise from the huge, 11-bladed fan. Surprisingly, this is supplemented by a thermostatically- controlled electric fan on cars destined for certain markets (not including the UK).

The gearing has clearly been chosen for optimum performance, but the car's cruising speed is very much at the driver's discretion. We found it would settle happily enough with 200km/hour showing on the speedometer - a true speed of just over 120 mph; even at this pace, there is remarkably little wind noise. The coarsely-calibrated speedometer was found to be almost dead accurate up to 100 mph, only at the top end of its range did it exaggerate to any significant extent (to the tune of 4 per cent at a true 130 mph).

As mentioned earlier, the new three-speed torque-convertor transmission is very much smoother than the earlier four-speed unit, which is still fitted to some of the smaller models. It is also quieter, both in itself and in the way it avoids buzzing the engine at town speeds.

With the selector lever in the drive range (D), kickdown changes to intermediate are possible below 85 mph - an arrangement which makes for excellent overtaking ability in fast-moving traffic. In the same way, kickdown changes into low may be executed at any speed below 41 mph.

The tunnel-mounted lever features the usua Mercedes zig-zag gate; it is precise and easy to use, and is illuminated at night. Using it to hold intermediate makes it possible to kickdown to low at speeds as high as 47 mph - a useful facility if the car is to be rushed along winding roads.

The remainder of the driveline is totally unobtrusive. A limited-slip differential is available as an extra-cost option in certain markets, but not in the UK. None was fitted to the test car and we doubt whether it would be needed in any ordinary conditions. However, it must be admitted that the roads were perfectly dry for the whole of the test period.

The test car was marred by a fairly high-frequency vertical shake (enough to induce appreciable steering column vibration) at speeds between 90 and 110 mph. This may be caused by imbalanced wheels; certainly, other examples we have tried did not misbehave in this way.

Ride and Handling

Extra length makes rear compartment extremely commodious, but a third passenger still has to be contend with obstructive transmission tunnel. Note way door trims curve up towards rear.

There is little that can be said about the ride except that it is excellent. true, its quality at low speeds isn't soft in the American sense, but most owners will like it all the better for that. In any case, the sumptuous seating ensures that passengers will not be subjected to the least discomfort.

Road-noise insulation is somewhat less impressive, there being an appreciable amount of tyre rumble and bump-thumping over some of the nobblier surfaces. To put this into perspective, we would say that the car compared unfavourably with the BMW 520i in which we journeyed to Stuttgart.

One seldom expects light and responsive handling in a car of this size, yet this is an area where the 450SEL truly excels. Although very stable in a straight line, the model feels beautifully balanced when cornered hard. There is no question of the driver having to lug it around corners; on the contrary, it can be set-up in a slightly tail-out attitude with no trouble at all. Roll is moderate and there is surprisingly little squeal from the tyres.

The power-assisted steering plays an important role in all this. Of Daimler-Benz manufacture, it is beautifully light and quick without being at all hyper-sensitive. It has ample feel, yet it is totally free from kick-back and fight.

Another valued feature is the excellent lock. Despite its considerable size, the 450SEL has a turning circle of less than 36ft between kerbs (mean figure). On a slightly critical note, the power steering pump is just audible when manoeuvring at very low speeds.


Disc brakes are used on all four wheels. Those at the front are internally vented, whilst those at the rear feature shoe-type parking mechanisms (the dished naves of the discs double as drums). The use of four piston front calipers allows both of the hydraulic systems to serve the front wheels.

As is customary in Daimler-Benz products, pedal efforts are low (some may think too low), with 20lb sufficing for a deceleration of 0.45g, this is all that is likely to be called for in normal circumstances.

A peak deceleration of 0.93g was achieved, using an effort of only 40lb. At this stage, the front wheels were just locking. Further increase in effort simply resulted in decreased efficiency.

When comparing these results with similar ones obtained at MIRA, it must be borne in mind that the proving ground's test surface has a higher coefficient of friction than that of most public roads. In the circumstances, we regard the result achieved by the 450SEL as being totally acceptable.

As may be gleaned from the results of the accelerated fade test, there is nothing to fear on this score. Even so, we did experience some rumble from the fronts when braking moderately hard from maximum speed.

Left-hand-drive models feature a foot-operated parking brake. This is remarkably effective, achieving a deceleration of no less than 0.59g from 30 mph. On a freak gradient, adjudged to be around 1-in-3, it held the car with consummate ease. Likewise restarts were achieved without the slightest difficulty.

Fittings and Furniture

The 450SEL's sumptuously upholstered seats are trimmed in nylon velour. A plain-weave material is used for the pleated centre panels, relieved by the use of a transversely ribbed pattern for the sides. A similar, plain nylon velour is used for the door pads. The overall effect is most comfortable and pleasing to look at. Available as a no-cost option is leather trim.

Folding centre armrests are provided at both front and rear, the former being affixed to the right-hand (passenger) seat. There are also large armrests-cum-pulls for all four doors, plus a roof-mounted grab handle above each opening.

As on other Mercedes models, the driver's seat is adjustable both for reach and for height. The front passenger's on the other hand, has no height adjustment. Both backrests are adjustable for rake, infinitely variable geared mechanisms being used for this purpose. Of necessity, the later are low geared; what makes things difficult is that there isn't a great deal of space between the knobs and the console.

First aid kit (supplied with car) in a well on right of rear shelf.

Front and rear seats all have adjustable head restraints. All are said to be removable, but we were reluctant to apply the effort this calls for. With front headrests removed, there is ample space for the backrests to be lowered flush with the rear seat cushion (not possible with the headrests in place).

A luxurious cut-pile nylon velour covers the floor. It is also used extensively elsewhere, examples being the sills, cowl sides, console, undersides of the scuttle and the rear shelf.

Somewhat in contrast, the major part of the roof is trimmed in grained and perforated pvc. The whole of the periphery of the roof, together with the pillars and and the peripheries of the doors, feature enormous plastic mouldings which are designed to protect the car's occupants in the event of an accident. Likewise, a crushable moulding forms the basis of the belt-rail crash pad and the instrument cowl.

The lower portions of the front door mouldings are shaped to form large, semi-rigid pockets. Although susceptible to kicks and scuffs from careless feet, these are very useful. Less pleasing is the way all four mouldings curve upwards towards the rear at the base of the windows - a feature which considerably reduces the useful area of glass. This, together with the enormous thickness of windscreen pillars, is the models biggest shortcoming. In fact, it has a distinct ESV air about it.

Inertia-reel seat belts form an integral part of the car's interior. The reels for the fronts, together with a major part of the belts themselves, are neatly concealed behind the pillar trim pads.

At the rear, the reels and "inert" parts of the belts are similarly hidden. The system works well, being both neat and easy to use. Furthermore, the geometry and the tensioning are exactly right. Alas, the rear installation is not available on UK models.

Dashboard layout.


The 450SEL lacks little in the way of equipment. All four doors have courtesy switches, operating separate lamps for rear and front. The latter incorporates a delay system which keeps the light in operation long enough for the occupants to don their seat-belts and for the driver to find the ignition and lighting switches (5 or 6 seconds at normal ambient temperatures). A fascia-mounted switch enables the rear interior lamp to be operated independently of the doors.

Headlamp wash/wipe system is both neat and effective. Note positioning of jet on bumper top.

Electric window lifts are fitted as standard. In addition to a separate rocker switch on each rear door, there is a group of four similar switches at the front, on the console (within easy reach of both driver and passenger). Also on the console is a push-button which can be used to render the rear window lifts inoperative (for child safety purposes). Another good feature is provision for actuating the window lifts when the ignition key has been removed (the normal supply being via the ignition switch). This is achieved by means of an alternative supply, which is routed through a micro-switch in the drivers door jam. Thus it is necessary only to open the driver's door to actuate the windows.

Wipers have two continuous speeds, plus an intermittent wipe facility. The enormous arms and blades clear a good area of screen. Extra in some countries, but standard on UK models, is a headlamp wash/wipe system. Controlled by the same foot pedal as the windscreen wash/wipe, it operates only when the headlamps are on - very neat and extremely effective.

Naturally, a heated rear window and a hazard warning system also come as standard. Less common items are built-in fog lamps and rearguard lamps. These are actuated by axial movement of the rotary switch which controls the main lighting system. The rearguard lamps are built into the rear lamps clusters; likewise, the fog lamps share the same lenses (but not the same pattern) as the headlamps. Featuring H4 halogen bulbs, the latter are adequate rather than sensational. We also found that the dipped beams troubled oncoming drivers - this despite the fact that the lamps seemed to be correctly aligned and the rear of the car was quite lightly laden.

There is a massive door mounted mirror, fully adjustable from within the car. Padded and spring-loaded for safety reasons, it is very effective and never loses its setting.

Front compartment is as luxurious as rear. There are separate heating controls for each side of the car. Note duct that feeds air into door cavity.

Although very much a luxury, an item which we find most pleasing is the central locking system. Standard on this model, it enables doors, boot and fuel filler to be secured simply by locking the driver's door.

Surprisingly there are no door markers - not even reflective strips. On the other hand the rear doors are provided with child-proof locks.

Access to the front is good; thanks to the extra width of the doors, that to the rear is even easier, although there are deep sills to contend with in both instances.

The rear compartment is truly cavernous, with an abundance of room in every direction. Front seat occupants are also well cared for. The driving position is good, although some people may think the non-adjustable steering wheel too large and a mite too high. A driver of average height has difficulty in seeing the offside front corner, but reversing presents no special problems.

Stowage space for odds and ends is plentiful. In addition to the door pockets, already mentioned, there is a lockable glovebox on the right of the fascia (left-hand-drive car). There are also nets on the backs of the front seats and a sizeable well atop the console.

No air conditioning equipment was fitted to the test car. The heater, however, behaved very well. Ample heat is available, and the distribution is good. Particularly appreciated is the ducting of hot air into the front door cavities - a feature which effectively demists and de-ices the side windows. So far as could be ascertained, there is no provision for ducting hot air into the rear footwells. The blower has four speeds, all but the highest of which (labelled "Defrost") are unobtrusive. Sensibly, the blower is arranged to boost the flow of cold air through the face-level vents.

On the test model, additional ventilation was available simply by opening the electrically operated sliding roof. Surprisingly, this did not result in undue buffeting, even at speeds of up to 120 mph.

Large boot is sensibly trimmed. Note strap for holding spare-wheel cover in open position. Reflective triangle, clipped to boot lid, may be dismounted for siting away from car.

The boot is large, but has a deep sill. Sensibly, its floor is covered with a non-skid rubber mat. Good quality loop-pile carpet is used elsewhere. Underneath the mat is a hinged flap which conceals the spare wheel. A strap is provided to hold the flap open while the wheel is being manipulated. A screw-pillar jack is clipped to the left of the wheel. There is also considerable space around it for stowage of odd spare parts and equipment.

Amongst the car's safety equipment is a reflective triangle. This lives on the inside of the boot lid - a position which allows it to be clearly seen simply by opening the lid. It can easily be dismounted for siting away from the car.

Typical of Daimler-Benz attention to detail is the recessing of the catch for the rear-hinged bonnet. Another example is the provision of two safety catches for the lid itself. Although seemingly inordinately complicated, the under-bonnet layout is accessible enough. Certainly, the items requiring routine attention could hardly be better sited.

Impression of Right-hand-drive Model

As mentioned earlier, we borrowed a right-hand-drive model for photographic purposes. As there are a number of differences between the two versions, we feel that a few notes are in order.

First thing to be noticed is that a pull-out handbrake replaces the foot-operated parking brake. Although slightly less effective (we recorded a peak deceleration of 0.27g from 30 mph), it is good for its type.

Another difference is that the left-hand drive model's tachometer is replaced by a clock. Since it makes sense to leave the automatic transmission to its own devices, this may be a reasonable move. In any event, we suspect that not all left-hand-drive models are fitted with a tachometer.

The UK model lacks the facility for actuating the windows with the ignition off (no second micro-switch in the driver's door-jamb). Another petty economy is the failure to transfer the bonnet release from left to right.

Tinted windows are standard on cars destined for the UK. Elsewhere this is classed as an extra-cost option.

Because the front seats have been interchanged to provide the driver with the height-adjustment facility, the backrest adjustment knobs are positioned outboard. Lack of clearance between them and the pillars makes actuating even more difficult.

There is no supplementary cooling fan. However, the model retains both the engine and transmission oil coolers.

Finally, we would say that the photographic car seemed quieter mechanically. Shod with Pirelli CN36 tyres, it also seemed to suffer a little less from road induced noise.