Cadillac Seville vs Mercedes-Benz 300D: transatlantic oil tankers

By Martin Buckley

| 3 Jan 2024

Classic & Sports Car – Cadillac Seville vs Mercedes-Benz 300D: transatlantic oil tankers

Cadillac was in a pretty dark place by the early 1980s, scrabbling to reinvent itself in an era of legislation that seemed to stand against everything the name once represented.

The powerful, glamorous behemoths of the 1950s, ’60s and early ’70s were gradually being replaced by a downsized, rather apologetic breed: vehicles that had neither the credibility of the increasingly popular imported European luxury cars, nor the gravitas and presence of the giant land yachts that had once been such potent symbols of American cultural power.

The 1976 announcement that Cadillac would not be building any more convertibles (after the demise of the huge 8.2-litre Eldorado) had already come as a shock.

From 1980, the Cadillac Seville’s standard engine became a V8 diesel

In the end, reports of the death of the great American ragtop had been greatly exaggerated (they went on to make a comeback in the ’80s), but it was still a graphic illustration that even America’s most illustrious marque was not immune to the changing mood around size, safety and smog.

Yet the process of bringing its cars down to size had started promisingly. The 1975 Seville was an ‘international’ Cadillac that garnered complimentary reviews worldwide for its manoeuvrability, refinement and crisp, tasteful styling.

Fully comparable with the Mercedes-Benz S-Class in most respects, this spectacularly successful luxury sedan was not an ‘entry-level’ car, but marketed as an exclusive, premium product.

The Cadillac Seville’s curious ‘bustle-back’ look was inspired by 1930s English styling trends

This was a genius move. Rather than pricing according to size and wheelbase (the more car you get, the more you pay), Cadillac pulled off the trick of selling its most compact-ever offering for a significantly higher sticker price than its traditional ‘full size’ models.

Basking in this achievement, the bosses at General Motors’ prestige division noted with satisfaction that eager new Seville customers were trading in their Mercedes, BMWs and Jaguars against the compact Cadillac.

But there was no time for complacency: behind the scenes there was consternation as to how the success of the ’76-’79 Seville might be followed up, particularly in light of new, tougher Federal legislation on fuel consumption.

Stepping into the Cadillac Seville, you are greeted by swathes of brown leather

Corporate Average Fuel Economy (CAFE) rulings, coming into effect in 1978, set the average US mpg for each manufacturer – both domestic and imported – at 18, a figure due to rise incrementally to 27.5 by 1984.

Those who failed to meet the standards had to pay a fine of $5 per 10th of a mile under the target, plus a ‘gas guzzler’ tax.

This legislation had real teeth, and resulted in Jaguar being the first to be fined: £5m in CAFE penalties, with an additional £16m in gas-guzzler tax collected by the IRS.

The Cadillac’s 5.7-litre V8 engine produces fewer than 19bhp per litre

Cadillac’s answer was to build a rationalised range of lighter cars on GM’s new ‘E-body’ chassis, where the Seville shared front-wheel-drive and suspension technology with a new downsized version of the Eldorado ‘personal luxury’ coupe.

Not only were these models the first fully independently suspended Cadillacs, but they were also the first to be intelligently packaged, with superior internal space to the outgoing rear-wheel-drive Seville.

Even more radical was the decision to go diesel: for 1980, the standard engine in the new front-drive Seville would be the 5.7-litre V8 oil-burner developed by Oldsmobile for its 1978 Delta 88 and offered as an option in the last of the rear-drive first-generation Sevilles.

The Cadillac Seville lacks much in the way of driver reward, but the front-drive chassis feels secure and relatively nimble

After decades of cheap fuel, the idea of fitting a diesel in any type of American private car – never mind a Cadillac – was completely alien to the buying public.

Yet in other respects the theory was sound: as well as being cheaper to operate, diesels were not subject to the same emissions regulations as gasoline engines.

When offered as an option across the full range of large-body Cadillac, Chevrolet, Pontiac, Oldsmobile and Buick models, it also looked like a handy way of keeping down that all-important corporate average mpg.

The filler cap is hidden behind the Cadillac’s numberplate

But with time short – and the GM purse strings tightly held – the scene was set for an engineering disaster.

The trouble stemmed from the fact that the Oldsmobile-designed LF9 was not an all-new engine but a diesel-burning adaptation of its ubiquitous 350cu in V8, with cylinder-block reinforcements to take the loads associated with compression-ignition units.

Looking to cut costs, the Oldsmobile engineers failed to give the engine sufficient head bolts: the rash of gasket failures – along with a litany of other reliability issues, including broken crankshafts, cracked blocks plus injector and fuel-pump failures – quickly emerged.

The LF9 was so bad that unhappy buyers got together to launch a class-action lawsuit against GM to recoup 80% of the cost of new engines.

The Cadillac Seville has a thermometer beneath the door mirror

In any competition for ‘worst engine ever’, it would be hard to find a more promising candidate, although the gutless 4.1-litre petrol V8s and V6s fitted to later Sevilles run it close.

It is hard to know how much of this toxic reputation was public knowledge when the first ‘bustle-back’ Seville made its debut at the 1979 Frankfurt show, but it may well have been significant that a 145bhp, 6-litre petrol V8 was a no-cost option that many Seville buyers appear to have preferred to the anaemic 105bhp diesel, presumably on the basis that if you can afford a Cadillac, you can afford the extra fuel.

The bustle-back or ‘slant-back’ look was the parting shot of GM styling boss Bill Mitchell, who for some years had been guiding his designers – headed by Wayne Kady – towards this bizarre, sheer-sided tribute to the English ‘Empress Line’ styling of the 1930s and ’40s.

At $20,400, many buyers hated the new look, but just as many loved it: enough to cause Lincoln and Imperial to come up with their own versions of the bustle-back for 1981/1982.

The innovative climate control system is one of the Cadillac Seville’s many gadgets

Mercedes-Benz made its money out of thirsty petrol-engined cars, many of them V8s, but it also had a history of producing diesel-engined passenger vehicles going back to 1936, and had built two million oil-burning mid-sized saloons for the post-war market as the end of the 1970s approached.

Thus where others saw a problem, Mercedes saw an opportunity.

Half the cars sold by Benz Stateside were already diesel 240 and 300 W123s by 1981, and there was even an America-only turbodiesel C123 coupé (the 300CD) and the turbodiesel 300SD W116 S-Class.

The Cadillac Seville’s hubcaps were designed to mimic alloy wheels

From 1981-’85, Mercedes sold only diesel-engined 123s in the USA.

The 300D was powered by the now-familiar OM617 five-cylinder diesel.

This 80bhp (later 87bhp) four-stroke, indirect-injection unit was as rugged as the GM diesel was frail.

It had an alloy cylinder head, an iron block, a chain-driven overhead camshaft, six main bearings and an in-line Bosch distribution pump.

The Mercedes-Benz 300D (left) and Cadillac Seville were diesel-powered answers to America’s ‘gas guzzler’ tax

Its odd number of cylinders was based around the notion that a ‘five’ is smoother than a ‘four’ but not as bulky as a ‘six’, with its potential for torsional problems because of the long crankshaft.

This was an idea engineers had been toying with for decades, and was already an established concept in the realm of large commercial diesels.

In naturally aspirated guise, the OM617 was first seen in the W115 in ’75 and the W123 a year later.

In the UK we only got a non-turbo 300D in saloon and wagon forms.

The idea of a diesel Mercedes was far from alien by the time the 300D arrived

Ordered via Mercedes-Benz UK, the 1984 300D auto pictured here was bought for the use of Indian prime minister Indira Gandhi.

After her October 1984 assassination, it was never delivered and only resurfaced a few years ago in the hands of Mercedes enthusiast and executive producer Aviv Screwvala.

It could be the highest-specification 300D in UK captivity, fitted with self-levelling rear suspension, air conditioning and engine sump-guards: the ideal specification for a car that would be travelling in hot conditions on poor roads with a hefty human load.

The Mercedes’ asthmatic diesel ‘five’ had 80bhp initially, rising to 87bhp in 1979

Diesel power only added to its versatility in a territory where the quality (and availability) of fuel could not always been counted on.

Even its wheels are interesting, rare light-alloy rims that allow the fitting of the colour-coded chrome embellishers.

In other words, not the usual Fuchs ‘Mexican hat’ type but essentially alloys designed to look like steels, yet still with the benefits of reduced unsprung weight.

With all those options, we can be confident that an equivalent US-delivered 300D would have come in at well over the $24,000 Cadillac required for a diesel Seville by then.

The Mercedes’ curious alloys do a passable impression of steel wheels

As a value-for-money offer the American car trounces the Mercedes, be it in standard or fully optioned form: self-levelling rear air springs, cornering lights, puncture-proof tyres and reach/rake steering-wheel adjustment were all standard, and that was over and above the expected powered locks, climate and cruise control, self-closing bootlid, power seats and all manner of bells and whistles.

Even the keyholes in the Seville’s doors were illuminated at night, and if you invested in an Elegante model – such as this one, property of collector Fredrik Folkestad – you got the dubious benefit of a two-tone paint finish, fake alloy wheels and a wreathed Cadillac emblem atop that chromed radiator grille.

Fredrik’s car, recently imported from Sweden, has the optional ‘Touring’ suspension offered to customers who wanted a more European feel to the ride and handling.

The Mercedes’ handsome yet understated profile is timeless

Inside, the brown MB-Tex used throughout the 300D makes it feel as austerely practical as the buttoned leather of the Cadillac’s twin sofas is regal.

Electric windows all round give the German car a hint of luxury, but the Cadillac’s roomier interior, with its flat front floor, is of a completely different, chintzier sensibility.

Yet it is undeniably welcoming and comfortable: a place where, beyond the fake wood and chrome details, the boxy architecture of the dashboard is clear and logical.

Yes, its skinny ribbon speedometer was an anachronism by the early ’80s, ditto the column gear selector for the three-speed automatic gearbox, but that was how Cadillac customers wanted it.

Electric windows are among the few concessions to luxury in the Mercedes-Benz 300D

The 300D’s engine, with its polished cam cover, appears less utilitarian than most Benz diesels, whereas the Cadillac powerplant looks as industrial as any other American V8.

On start-up, both are relatively knock-free, but cannot disguise their oil-burning origins. Under way, the Cadillac is by far the more refined of the two, with only a slight vibration to let you know it is running and no great indication (with bonnet shut and frameless doors closed) you are driving a diesel.

This almost distracts you from the tragic lack of acceleration.

Gearchanges are imperceptible, but using kickdown only serves to make the engine rumble slightly more loudly rather than urge the car forward any faster.

Fitted with air-con, this Mercedes 300D was primed for a life spent travelling in hot conditions

On paper, the 300D doesn’t do much better in a straight line.

Yet, even as an auto, acceleration in the Benz borders on the semi-brisk, and it gathers speed in a fairly fuss-free way that is far removed from the usual derv W123 experience.

The four-speed automatic was strengthened to take the diesel’s torque and is recalibrated to pull away in first gear rather than second, although to avoid ‘creep’ it holds itself in second at standstill until the throttle is squeezed.

The handling and ride are probably what make this 300D so different to most other 123 saloons.

Its heavy-duty springs with self-levelling mean that it sits around 1½in higher than a normal 300D, and gives an exceptionally smooth and compliant ride, regardless of the load or the number of passengers. Aviv confirms it takes London speed bumps beautifully.

The Mercedes 300D has a spacious rear bench

That said, I suspect the Seville would be its equal in terms of smoothing road-surface irregularities – and rather better at smothering road noise.

The Cadillac is a quiet car even by modern standards, with few rattles.

It is hard to be definitive about ‘build quality’, but the fit and finish of the Seville don’t look far behind the Mercedes, at least superficially.

Neither is the handling. Yes, the steering is lighter than the surefooted 300D, but it has some feel and is reasonably responsive.

With its front-drive and relatively modest levels of lean and wallow, the Cadillac corners faithfully and reassuringly, but with a more detached and expensive feel than the Mercedes.

Heavy-duty springs were added to this Mercedes 300D in preparation for the armour-plating that was never fitted

With almost 200,000 built through to 1986, the Seville was a commercial success but a reputational failure, perhaps the most ‘malaise’ of all Cadillacs – if you acknowledge that the dreadful Cimarron was just a tarted-up Chevy.

It certainly didn’t measure up to the ‘standard of the world’ mission statement that had underpinned the marque for decades.

That title had long since gravitated to the Germans, and to Mercedes-Benz.

The US industry had squandered decades on a formula of annual sheet-metal restyles garnished with crowd-pleasing luxury features.

The Mercedes 300D bolstered the German marque’s reputation for reliability

In contrast, the 300D was the product of a firm that had laboured away stoically at safe, highly drivable and far more durable-than-average vehicles to a straightforward recipe that made concerns about marketing and famously high prices entirely subordinate to engineering excellence.

If Cadillac built what it thought you wanted, Mercedes built the car it knew you needed, leading customer taste rather than pandering to it. You either got it or you didn’t.

In North America, an increasing number of buyers did, and when thoughts turned to the idea of a diesel luxury car, no maker was in a better position to lead the way.

‘The Mercedes gives an exceptionally smooth and compliant ride, regardless of the load or the number of passengers on board’

Though not exciting, the 300D was possibly the first diesel you might have bought out of choice, rather than necessity.

Maybe, with a blanket 55mph speed limit, the sheer sloth of the Seville didn’t matter that much on home turf.

Possibly, but the reliability problems most certainly did.

It’s a better car than it looks – which perhaps isn’t saying much – but with a prettier body and a decent petrol V8, it could almost be desirable.

Images: John Bradshaw

Factfiles

Cadillac Seville

Sold/number built 1979-’86/198,155 (all)
Construction steel perimeter-frame chassis, steel body
Engine all-iron, ohv 5737cc diesel V8, fuel injection
Max power 105bhp @ 3200rpm
Max torque 205Ib ft @ 1600rpm
Transmission three-speed auto, FWD
Suspension independent, at front by wishbones, torsion bars, telescopic dampers rear trailing arms, air springs; anti-roll bar f/r
Steering power-assisted recirculating ball
Brakes discs, with servo
Length 17ft (5202mm)
Width 5ft 9in (1801mm)
Height 4ft 5in (1379mm)
Wheelbase 9ft 5in (2896mm)
Weight 4184Ib (1898kg)
Mpg 20-24
0-60mph 19.7 secs
Top speed 83mph
Price new $20,400
Price now £6-10,000*

Mercedes-Benz 300D

Sold/number built 1976-’84/324,718
Construction steel unitary
Engine iron-block, alloy-head, sohc 3005cc diesel ‘five’, fuel injection
Max power 87bhp @ 4400rpm
Max torque 127Ib ft @ 2400rpm
Transmission four-speed automatic, RWD
Suspension independent, at front by wishbones rear semi-trailing arms, self-levelling; coil springs, telescopic dampers, anti-roll bar f/r
Steering power-assisted recirculating ball
Brakes discs, with servo
Length 15ft 5in (4725mm)
Width 5ft 8in (1786mm)
Height 4ft 7in (1438mm)
Wheelbase 9ft 1in (2795mm)
Weight 3186Ib (1445kg)
Mpg 24-28
0-60mph 17.7 secs
Top speed 96mph
Price new £11,146
Price now £10-30,000*