Performance
Most acceptable for a diesel

The 93x92mm, 2,500 c.c. engine is transversely mounted like its petrol brothers, and produces 75 bhp (DIN) at 4,250 rpm, with a hefty 111 lb ft maximum torque at 2,000 rpm. The five-speed gearbox is arranged so that fifth is a normal top gear rather than an overdrive. With overall gearing of just over 22 mph per 1,800 rpm, the highly creditable (for a diesel of this size) 97 mph maximum speed corresponds to 4,400 rpm, suggesting that the car is if anything a little under geared. The difference is in fact too small to matter, and one can understand why the makers have gone to the bother of fitting what sounds like a sports sort of gearbox to a homely diesel. It's done, paradoxically enough, for the same reason that one fits such a box to a sports car - because of a rather narrower-than-usual power band. 4,250 rpm is not high as power peaks go, and although it is possible to rev at 4,750 before the usual diesel governor cuts in, there is little point in revving that high.
At the other end, the engine will pull, academically speaking, from 800 rpm, but one does not like to use it below 1,200 rpm. You need the five-speed to make best use of the fat middle part of the diesel power curve; the engine is not inflexible by diesel standards — provided the speed does not drop below 35 mph, you are happy to stay in top. But for best acceleration, the range of the box is welcome, and its ratios well chosen, as the revs to which the engine falls after changing up through the box at 4,250 rpm demonstrate — 22 mph in first corresponds to 2,500 rpm in second, 37 in second is 2,900 in third, 55 in third is 3,200 in fourth, and 73 in fourth is 3,300 in fifth.
The low first gear is necessary for much of the work which the car is likely to do. Re-starting on 1-in-3 was achieved, but with some hot lining smells from the clutch, even though the engine had to be revved only a little. In pure performance, the 2500 is really very acceptable for a diesel — and by that we mean that it is not really a sluggard by petrol engine standards. In fact that performance parameter beloved of the enthusiast, the 0-60 mph time (of 17.0 sec), is only made as slow as it is by the fact that one is beginning to feel the slowing effect of the governor as one approaches 60, so that it is better to change up to fourth beforehand. Gearchanging is easy — the change is light, a little rubbery, yet precise enough. We did however notice some weak synchromesh, surprising on this low mileage car, both loudly during the acceleration runs and not so loudly during ordinary driving. It is important not to be impatient about selecting first from rest, and one does well to make fairly accurately matched down-changes — an unusual requirement nowadays.
Like all big Citroens, the car is very much at its best — a quite delightful best — on the open road. It cruises easily at up to 90 mph, and its other virtues (and vices) combine to make it very relaxing on a long run. It isn't annoying in town - just rather harder work than some other cars.
How many of the usual diesel irritations does it have? The answer is "Not many." You get used to the power, which as we have said already is more than enough. It makes those seemingly undisguisable diesel taxi noises on tickover and remains undeniably diesel up to around 55 mph in top (2,500 rpm); thereafter it is beautifully smooth in sound and feel, apart from a surprising over-run rasp from the exhaust on changes up. Its diesel-ness is very obvious at up to 40 in top (1,800 rpm). On the other hand, Citroen (and presumably CAV going by the test car) have joined the narrow band of manufacturers headed by VW (and Bosch who incidentally are alternative suppliers to Citroen) who have succeeded in mellowing the diesel characteristic most annoying to the smooth driver - that abrupt cut in power when you lift off the accelerator (it isn't really a throttle on a diesel) during and, more important, as one approaches a change-up. The car is correspondingly easier to drive smoothly. One suspects that the credit is partly Citroen's, in providing the right sort of engine mounting characteristic, always more difficult with a transverse engine like this. Those of us who recall the 2500's predecessor (which wasn't good in this respect) are especially impressed. Once warm, diesels start marvellously quickly, but from cold there is the small penalty of time spent waiting for the cold start ignition glow plugs to warm up; in fairly chill "summer" weather, the car took only 12 sec before it would run, which is slighly (sic) better than our much-admired Volkswagen Golf diesel in the same temperatures.
Noise
Not too much of it

The car's engine noise has been mentioned already; it is a little tiresome in traffic, at slow speeds, but gets much better as you go faster. On the test car there was a surprising amount of wind noise, demonstrating once again that wind noise heard inside is not a function so much of shape as of sealing. The ride is superb, but the suspension is surprisingly noisy - bump-thump is rather higher than average.

Economy
Very frugal

As is proper for such a car, we began this Autotest by discussing the overall fuel economy - which is outstanding for a car of this size. The extra capacity has seemingly done no harm to this compared with the figure returned by the original CX diesel (31.8 mpg overall). With the help of our TransFlo fuel flow metering equipment we are now able to measure steady speed consumption on most fuel injection cars; the figures for the 2500 D are fascinating — nearly 60 mpg at a steady 30 mph in top gear, over 40 mpg at a steady 60 mph, and only a little under 40 at a steady 7O mph. We kept the meter going for a flat-out maximum speed lap, when the car returned 23.2 mpg — just for the record.
Filling diesels to the brim is always made difficult by derv's habit of frothing; the Citroen filler helps as much as possible by being very close to the tank, and of unusually large diameter. The 15-gallon tank gives a most useful range of never less than 450 miles — which is around half as much again as on most petrol cars - and up to close on 600 if driven gently.

On the road
Superbly stable

Citroen's thinking on steering and ride are well known. The steering is powered, very high-geared — only 2 1/2 turns lock to lock for a turning circles (sic) which at 35 1/2 ft between kerbs are remarkable for such a long (15ft 2in.) car - and has the added peculiarity of powered self-centreing, which straightens the wheels whenever you let go, even when stationary.
The high gearing, once you have got used to its almost over-twitchiness, is delightful, and is just what such a long car needs in tight places. With even more front-heaviness than before (nearly 71 per cent of the unladen mass is on the front wheels in contrast to 68 1/2 per cent on petrol CXs and 61 1/2 per cent on the more orthodox front-drive Princess), the car is of course an excellent straight runner. Citroen claim very high side-wind stability; we found it very good compared to most rear-driven cars, and not noticeably better than the better contemporary front-drive competitors. It is if anything a bit of a handful in strong winds, needing more than usual concentration because of the responsiveness of the steering. All cars, even the most stable, move in side winds; and although the CX moves much less than most, its steering is rather too responsive in slight corrections. You are reminded that for once, there is no direct mechanical connection between steering and front wheels.
This is a small criticism, because one gets used to it. The same applies to the total lack of any feel in the steering — feel is nice to have, but not nearly as essential as purists say, since accuracy is far more important, and a sensitive driver of experience "feels" what the car is doing through his organs of balance as much as through his hands. We are not so sure about the powered self-centreing. The ‘few times it is wanted are when parking, and even then the car's power assistance — in the normal sense — is all that is really necessary. There are more frequent times, when one finds oneself stuck in a traffic jam on a corner of any sort, when it is a small but noticeable nuisance. Let go of the wheel while you wait, and the steering unwinds, so that before moving off again you must re-apply some lock — the right amount of lock if cars are close on each side. We would rather do without it.
In spite of its front heaviness, the car does not understeer as much as one might expect, although generally speaking that is its ultimate fate if cornered to its limit. Decelerating in mid-bend generally has little effect, except on some occasions when cornering very fast when what may be an effect due to the car's suspension system can induce a surprise moment of oversteer. We only encountered this once on a closed track; it does not occur at any time in normal driving. There is some roll, but not too much.
Ride is generally superb, as ever. The car soaks up bumps in a fashion that is almost totally unknown to most other cars, and in this it will give the owner the greatest satisfaction. It has that most valuable attribute which ought to be found on all cars by now — self-levelling. It does the usual Citroen party tricks, sinking when you switch off, rising on re-starting, and of course has a really useful range of suspension height adjustment if the going gets really awkward. You learn to remember the sinking when parking beside a high kerb; it is possible to find that the driver's door of the Citroen you parked is impossible to open widely enough to get in again on your return. The ride is not perfect; it is arguable that the simpler system used by Peugeot is a better all-round compromise which does not suffer from the hydropneumatic system's occasional embarrassment, such as its now well-known sharp unreadiness over a hump – the front wheels, pushed up into the wheelarch, don't come down again quickly enough on the other side. The car is also surprisingly harsh over very sharp-cornered bumps. Overall however, it is magnificent; the ride is one of the principal joys of Citroen motoring.
Brakes are live-power assisted, and very responsive, almost too much so on first acquaintance; you get used to them however, and in most respects they are satisfactory. Being inboard, [this is nonsense - the CX's brakes are outboard] one suspects that they have cooling problems if used hard and often. Our fade test showed up a not unacceptable rise in pedal pressures needed, which is made more noticeable by the relatively small size and rather too rounded profile of the brake pedal, which accentuates apparent pedal pressure. There is also the comparatively small pedal movement too, which exaggerates the feeling of fade.
Working on the front wheels, the handbrake is an unusually powerful one. You can't lock the front wheels — not surprisingly — and up to over 0.4g is obtainable, depending for once more on the strength of the driver than anything else. The car can be held easily on 1-in-3 slopes, pointing either way, which is more than can be said for front-drive cars with rear handbrake svstems.

Behind the wheel

Commandingly relaxed

The seats seem at first rather too soft, but go on a decent journey and you come to appreciate them enormously. They are most relaxing and comfortable, giving most people a subtle amount of what feels like the right support at all times. Passengers appreciate the head restraints, saying that one can snooze in the car very easily. Tall drivers might be glad of a little more legroom; our six-footers found themselves a little knees-up, short of some thigh support. You tend to adopt a fairly reclined attitude if tall, which, these criticisms aside, is very comfortable.
Driving position is generally good, and one is made to feel very much in command of this large and bulky car. As the number of Citroen CXs (and DSs) with dented mid-sections suggests, it is a car whose length must be respected and remembered; it has got that excellently generous lock, compensating one for any awkwardness due to size but that lock means more sideways displacement on tight turns, so care and judgement are needed, Luckily, for once here is a manufacturer who has almost always provided little obstruction to view in any direction, at any rate on his bigger cars, so that visibility is good. It needs to be, because the extremities of the car are invisible from the driving seat. The big central wiper is a bold design feature which works pretty well on the effectively half-square proportions of the screen, but there is a large unswept "triangular" area in each top corner of the screen which is irksome for the tall driver.
The finger-tip driving minor controls work very well, with delightfully positive switching and that very sensible Citroen preference for non-self-cancelling wipers — which don't cancel when you don't want them to, and which can be switched off so easily thanks to the position of the switch
There is the usual CX rolling drum speedometer — a 1970s version of a 1929 Morris Minor idea — which works well enough, saving dashboard area. It is lit at all times, and we found the brightness too great, even in daylight when one could be distracted. On their petrol CXs, an electronic revcounter is available, occupying the other window in front of the driver. Since diesel engines don't use electric ignition (and probably because most diesel owners would not want one anyway), no revcounter is available for the 25OOD — but the window is still there, filled with the Citroen chevron — and lit as brightly as the speedometer. We would welcome a rheostat lighting control for this.

Living with the CX 2500 diesel

On the subject of brightness we as before applaud the superb interior lamp, which gives all the light one so often needs inside a car — other manufacturers please note. The car's air-blending heating system works superbly, and ventilation is good too.
As you should expect with such a long wheelbase, there is a proper amount of rear room; this is a true family car in the best senses of the phrase. The superb boot has that usual Citreon (sic) freedom from any intrusion, bags of space, and a shape that is ideally squared.
There are anomalies; the trip mileometer has an old-fashioned twiddle-and-push type of zeroing arrangement. One would welcome more instruments and less warning lamps ~ there are 16 of the latter on the test car, plus one blank, and only a fuel and a battery volts gauge to back up the speedometer. Elaborate air horns are fitted - very effective.
There is the excellent oil level gauge, a thing like an old-fashioned oil sightglass which gives a plausible reading when you are driving but which you are only meant to take seriously ten minutes after stilling the engine. The radio is now better mounted, in front of the dash instead of between the seats; there is an ashtray on top of it, whose spherical shape suggests anything but its actual purpose to first-time CX riders. We would find nothing in the handbook about how you are supposed to empty this; a vacuum cleaner may be the best way, since it doesn't seem to be removable.
Oddment space is provided by putting a thin wall across the circular spaces left for the absent window winders — the car has electric windows as standard - plus a small pocket on the right beside the oil sight glass, and a lockable swing-down glove bucket on the left.
The bonnet is self-propping, opening to reveal a beautifully tidy engine layout which is refreshingly accessible in most respects.

The CX range

In order of price, the CX 2500 Diesel Super comes second in the CX hierarchy (sic), above the base CX 2000 Super four-speed (£5,796) and below the CX 2400 Super five-speed (£6,480).
After that comes the CX 2400 Pallas five-speed (£7,131), the CX 2400 Pallas injection C-matic (semi-automatic gearbox £7,799) (sic – missing opening bracket), the fastest example which is the CX GTi five-speed (£7,776) and finally the CX Prestige injection which can be had in five-speed manual or C-matic two-pedal versions both priced at £10,416. For anyone interested, there are four estate cars all of them remarkable machines — two CX Safari and two Familiales, all with four-speed manual boxes only and with either 2400 petrol or 2500 diesel engines.

HOW THE CITROEN CX 2500 DIESEL SUPER COMPARES

The limited range of the diesel market in Britain (or rather British cars) and the corresponding interest abroad is obvious from our lists of possible Citroen rivals. In the case of the most recently announced contender — Peugeot's very interesting and remarkably satisfactory 604 Turbo - it is not to be made available in this country until January - but we do have the experience of the manufacturer's launch driving impressions to draw upon (which included a check of maximum speed which corroborated the maker's performance claims quoted).
Performance is not of first importance to the diesel buyer — but it makes a great difference to even the most patient driver if he has something approaching petrol urge to draw upon. The figures speak for themselves, and they point up once again the well-deserved and increasingly important (sic) of a properly-designed, more truly aerodynamic shape. To come virtually top in performance and economy is almost unknown in our Autotest comparisons - but,
pending a test of that Peugeot, the Citroen does it.

ON THE ROAD

All of these are largeish cars by European standards, and all are independently suspended on all corners. Ride is therefore at least good in all cases, and outstandingly good as far as the Citroen is concerned — and in the Peugeot cases (sic); in fact it could be argued that the Peugeot overall rides better than the CX because its simpler suspension is a better general compromise which does not get seriously caught out by any bump combination. For many applications, the Citroen is the only car here with the considerable advantage of true self-levelling suspension (the very long wheelbase special versions of the Mercedes are so equipped, but not the standard car). Only the 504 is not available with power steering. Being the only front-drive car, the CX is both the most stable and, to a lesser extent, the one which understeers most. Ford, Mercedes and Peugeot all use semi-trailing arm rear ends which will ultimately break away — but you must be driving in most un-diesel style to ?nd this out. Thanks to its superb power steering, the Merc just has the advantage in pleasure of handling terms, but only just - but one cannot complain about the CX.

SIZE & SPACE

With the 504 as the mildly odd-one-out in size — it is the only truly medium-size saloon amongst this bevy of larger cars - it naturally takes bottom of the list here. But it should be remembered that none of these cars are mean in space; that includes rear accommodation which in all cases is generous enough for a full average-family load. Compared with the others, the Citroen user will revel in an unusually generous and uncluttered boot, and he will not be disappointed by the ease of driving of the car compared with the others — that last qualification is important, because nearly all Citroens, and certainly the CX need much more familiarity than other cars before one is able to feel at home. Once this has been achieved, the very great comfort of CX motoring becomes obvious, and its virtues as a long distance cruising machine of great relaxation are almost indispensable.

FUEL ECONOMY is a diesel strong-point even if performances suffers compared with a petrol car. Citroen's latest big-engined diesel is one of the nicest we have driven.

Find out how nice in this week's Autotest

LIKE MERCEDES, the diesel for Citroen is its bread and butter. It was not always so as far as the cars were concerned; there was no DS diesel, and the development of the Citroen G35 (sic - they mean the C35) diesel van unit used in the CX did not appear until 1975. Peugeot's long-established domination of the French diesel car market must have been a spur to Citroen, and however late they responded to it, the change has been spectacular. Of course the growing importance of fuel economy and the more favourable price of diesel in France has helped greatly - but the fact that the production of CX diesels at the Aulnay plant is now around 50 per cent of the total speaks for itself.
With derv still taxed more heavily than petrol - at 42 pence per gallon against petrol's 37p - the case for running a diesel in Britain is not so clear-cut. Taking the excellent 31.5 mpg overall test consumption of "our" 2500 D against the comparable 23.5 mpg of the CX 2400 tested in July 1977, and bearing in mind that the petrol car (CX2400 Super) now costs £253 less, it would be a matter of at least 30,000 miles before the British owner of the diesel would start to save money. But the advantage is there; and regular readers of Autocar Road Tests will need no reminder that our overall fuel consumption generally reflects near-enough the worst possible consumption obtainable from any test car. The average owner will do much better - we would expect at least 35 mpg as a bottom limit for most owners.

HOW THE CITROEN CX 2500 DIESEL SUPER PERFORMS

OIL CONSUMPTION

(SAE 20W/40) negligible

BRAKING

DIMENSIONS

VERDICT

Economy is of course the strongest card in the diesel's hand, and all of these are mean cars by any standards. Economy is tremendously important today — but human nature being what it is, if an economical car can also be made pleasing to drive, it becomes doubly attractive. This combination has until recently been rare in diesel cars, simply because performance was so limited, and the response of the engine was characteristically demanding, at any rate for the driver normally used to petrol cars. The arrival of the five-cylinder 300D Merc marked the beginning of better diesels, although many would say that Daimler-Benz already made the most pleasant examples of the type in the shape of the similarly bodied 240D. Volkswagen's brilliant Golf diesel was the real turning point however - and in our opinion the Peugeot 604 Turbo and the subject of this text, the superb CX 2500 keep the new standard up. Pending a full Autotest of the 604, we would put the Citroen on top today — it merits a word you don't often hear applied to diesels — delightful.