"D" for Diesel Day

A Test in Germany of the Type 170D Oil-engined Mercedes-Benz Saloon by David Scott-Moncrieff

A visit to Stuttgart is always fun, old friends with whom to swap a yarn, good Neckar wine to drink and usually something new and arousing to drive. This year we made the pilgrimage in a very vintage 37a Bugatti, which reduced my friends at Untertürckheim to complete helplessness with laughter, and caused them to swear that as the years go by I get crazier and crazier. However this did not prevent them from loaning me one of their latest Diesel-engined passenger cars for a day. I must confess to looking forward to my D for Diesel Day with more than usual relish. This was partly because I had driven the very first Diesel car that Mercedes ever built, back in 1936, and partly because the technical Editor of a leading periodical to which I do not contribute had just taken several pages to prove, with illustrations, that diesel-engined passenger cars could never be either it practical or a commercial proposition. I was as yet undecided as to whether he should eat, his words sauté with pommes frites, or maitre d’Hotel with chopped parsley.

With true Teutonic punctuality the Mercédès was delivered to the door of my hotel at Marbach-am-Neckar exactly two minutes ahead of time, and what a very compact all-of-one-piece motor-car it looked! As we slid smoothly over the few miles between Marbach and Ludwigsburg two impressions were paramount. First, apart from the intermittent click, rather than knock when the car is at rest with the engine idling, the motor is astonishingly silent, a great improvement on the earlier models, and the roadholding is really outstanding. As a secondary impression, the acceleration, although far from sluggish, seemed disappointing after the exactly similar car (Model 170S) with a petrol engine. But then it would be hardly fair to expect a diesel car to accelerate as well as a petrol one. We stopped at Ludwigsburg to take a photograph of the diesel Mercédès in the inner courtyard of the old palace of the Kings of Würtemburg. We thought this particularly suitable as the heir to the throne of Würtemburg, if there still was one, is the chief engineer in charge of the research and development division of Mercédès-Benz who was responsible in the first place for the development of this Diesel car. In point of fact, he is fortunate in his choice of occupation, for there is always a good job for it first-class engineer—but just look at the unemployment among kings!

After Ludwigsburg we went off to look for a really bad road and found an absolute shocker near Tamm, and pasted the car over it far faster than was either kind or considerate. This emphasised several points, that the springing does not sacrifice flexibility to achieve first-class roadholding, there is no body sway and there is not a rattle anywhere. What’s more the doors shut, although it is a mass-produced body, with that soft click that is normally the prerogative of the most expensive custom-built coachwork.

It was about this juncture that I noticed, somewhat belatedly, that the steering has a three-position lock, i.e., completely free, completely locked, or, for those occasions when one leaves the car in a public garage, a position where the steering may be turned to shift the car by hand but the engine cannot be started. I consider this a most desirable refinement as my wife and I have both suffered from finding the battery “inexplicably” run down overnight in a public garage. Besides, if a garage attendant has to push a car by hand he is much less likely to transfer oil to the driving seat from his own.

I had already quizzed the driver about cold starting, as I hadn’t seen the car start first thing in the morning and had some grim memories of swinging my heart out on alleged “cold starting” marine diesels during the war. However, as far as Mercédès go, that’s a thing of the past. It’s beautifully simple, there is an electrically-heated plug in the ante-chamber of each cylinder. On the dash there is a three-position switch. At position I everything is cut off. At position II the heater plugs come into operation and position III energises the starter motor. On the coldest morning all you do is this—hold the switch at position II for about twenty-five seconds till a pilot light on the dash glows red, then turn on to position III and the engine unfailingly starts. That’s all there is to it. When I was driving the car the engine was already warm, so I simply turned the switch to position III and, even after an hour’s interval for an excellent lunch at the Goldenes Hirsche at Lauffen the engine started at a touch. This equipment as well as the injector mechanism and the electrical system are all made by the house of Robert Bosche.

We tested the car for maximum speed. It isn’t high, 100 kilometres per hour. This is a fraction over 62 m.p.h., but the car can be held at this speed for hours on end if necessary with no ill effects or even overheating. But in spite of the low maximum speed and not very exciting acceleration the diesel Mercédès is capable of excellent average speed due to its really first-class cornering and road-holding. I don’t think it’s generally known in this country but the chassis common to the 170D and the 170S (petrol engine) is about the fastest thing over ice and snow ever built, so in a hard continental winter one could take on all corners including those capable of almost double the speed.

Diesel-oil consumption is something quite phenomenal, over forty-four miles to one gallon! In every country I can think of, this fuel is cheaper than petrol, so, for anyone covering a large annual mileage a very large hole is knocked in one’s running costs. A world consumption record has, in fact, just been officially established by one of the cars between Stuttgart and Hamburg.

Now let’s take a look at some of the technical specification:—

Engine: Four cylinders, bore 73.5 mm., stroke 100 mm., 1,697 c.c., giving 38 b.h.p. at 3,200 r.p.m. Compression 19 to 1. Firing order, O.h.v., push-rod operated. Oil capacity, one gallon.

Car: Wheelbase 2,845 mm., front wheel track 1,310 mm., rear wheel track 1,342 mm. Overall length 4,285 mm. Overall width 1,620 mm. Overall height (un-laden) 1,610 mm. Ground clearance 205 mm. Weight of complete car about 1,220 kilogrammes. Gear ratio in top. 4¼ to 1. Tyres 5.50 by 16 balloon. Turtling circle 11 metres (33 feet, pretty good this). Suspension independent all round with transverse leaf spring in front and coils behind. Tank capacity 37 litres, reserve three litres. Approximate mileage on one tankful 570 kilometres (about 360 miles). Lighting 12 volt. Four speeds. Top speed in third gear 75 k.p.h. (about 47 m.p.h.).

Altogether D for Diesel Day was a very pleasant day’s motoring. There have, frankly, been more exciting days, for example that fabulous unforgettable day nearly a quarter of a century ago when, barely nineteen years old, I drove a “36/220” “mit kompressor” for the first time in my life. But all the same I enjoyed every minute of my day with the diesel car. Like almost everything Daimler-Benz A.G. have ever built it has it thoroughly well-bred feel, all controls are positive and it’s a pleasure to drive. As we slid effortlessly through the vine-covered terraces of the Neckar valley, an exact analogy sprang to mind. Driving the 170D was comparable to savouring a wine of lesser vintage from a château of repute, not a grand vin, but utterly sound and a joy to the palate. I have, indeed, only a few serious criticisms of the car. I would prefer it upholstered in leather. At the price it sells for in Germany, 90,000 marks (around £700), they should be able to afford it when leather becomes available. And although there is excellent luggage space in the locker I would much prefer the back to let down and form an emergency platform rather than being, as it is at present, hinged from the top. I would also like a sunshine roof, but this is a feature on which German coachbuilders have never been keen, usually, I suppose, because they offered you a full cabriolet as an alternative.

But, taking it, by and large, for extreme economy, very robust construction, and superb roadholding and springing it’s hard to beat. So it’s not surprising that the works are going full chat and their order book is full for a very long time to come. And this is a fact in which I unashamedly rejoice, for only this morning, I got a letter from Alfred Neubauer saying that Germany had been officially re-admitted to International Racing. This must mean that, for every 170D that is sold, a few marks or some fractional sum thereof goes into the kitty against that day when a pack of lean white cars streak past, their blower’s screaming with the triumphant note that we have waited for over a decade to hear again.