(Updated 5/13/2026) The great irony of Olds’s introduction of its new big diesel V8 cars is that it came out just shortly before the only other large diesel sedan: the Mercedes 300SD. Like the Olds, the big Merc’s engine was developed specifically with the US in mind, to meet the demands of CAFE as well as the growing demand for import diesels. In fact, the 300SD was not even sold in Europe, as a diesel S Class would have been hard to swallow there, where diesels still had a lowly image of taxis, farmers and cheapskates.
But the US market was different in many ways, and the 300SD, especially in its next generation, the W126, became a bigger hit than Mercedes ever expected. And with its excellent performance, triple digit top/cruising speed, and 25+ mpg efficiency, that was not really all that surprising. Never mind its durability, which was presumed to be great then, but turned out to be utterly legendary.
Also not so surprisingly, the approach Mercedes took was quite different than Olds, as well as the outcome.
Of course Mercedes had a major head start in passenger car diesels, having built them since the 1930s. But the approach to building a more powerful one was quite new, at the time: turbocharging. That became increasingly ubiquitous, but up to this time it had not been done in a regular production car. The benefits compared to a larger, heavier naturally-aspirated diesel like the 5.7L Olds V8 were numerous: it was considerably lighter, generated about equal hp from only 3.0L, and had increased efficiency, as forced induction invariably does, by making the effective compression ratio higher as well as reducing internal friction compared to an equally powerful NA engine.
0-60 came in 12.7 seconds, but because of being a bit slow off the line, that number does not do justice to its mid range performance. The 0-80 sprint took 24 seconds. The 0-60 beat the Olds by almost two seconds. And its top speed, which it could safely cruise at, was 110 mph. Given how slow diesels invariably were up to this point, this was all a revelation.
Of course the 300SD was three times as expensive as an Olds diesel, but that was the reality back then, regardless of what engine was under the hood. But what was interesting is that Mercedes diesels cost less than their gas counterparts, and in the case of the 300SD, it was faster than the 280SE. No wonder diesels soon made up over 80% of US Mercedes sales. Meanwhile, Olds charged some $750 more for their diesel.
Here’s an accompanying article explaining the engineering of the new turbocharged Mercedes 5 cylinder diesel.
I worked as a valet parking attendant at some ritzy east-coast country clubs during the era of these cars, and boy, did we see these by the ton, along with their very smug owners.
The car was an absolute bank vault, but it didn’t accelerate so much as it “gained momentum”. The W123 300D-T was about 700lbs. lighter, and I liked them a lot better, but according to what Google is telling me, they somehow weren’t significantly faster.
No way was there a 700lbs difference.
The 300D turbocharged sedan was listed at 3450 lbs.
The 300TD wagon at 3635 lbs.
the 300SD at 3705 lbs.
And the new W126 300SD lost weight, down to 3650 lbs.
(curb weights per the factory, US versions)
0-60 in 12.7 seconds is “gaining momentum” pretty briskly, for the times.
When cost is no object, when you really are “engineered like not other car in the world”, and when you superimpose that on a high-end version (American spec S-class) of your premium product, it’s easy to do the right thing and make a profit.
That said, yes, the Merc 5-cylinder turbodiesel was brilliant in the late 1970s. It was so good (relative to other cars of the malaise era), that it’s performance alone warranted the high price.
Time would prove the “new” 300SD grossly superior to the “new” Olds 350 diesel.
But, as an aside, my contrarian impulses compel me to point out, that was not the case when comparing gasoline V8 450SE vs colonnade Cutlass 350 in 1973 (the road test can be found here on Curbside Classic).
In 1978, a 1978 450SE vs a 1978 Delta 88 350 with the handling suspension, the Olds was comparable overall, IMO. It was superior in several respects that people value (room, HVAC, quiet acceleration to 60), and cost much less. The Benz had infinitely better seats and dashboard, and much better high-speed driving characteristics (which in crowded, 55mph, Long Island were not readily enjoyable).
GM’s best held it’s own and then some against MB’s best. Not too shabby for GM.
Of course, I would definitely pick the Mercedes, if offered a choice. But if I had to pay with my money, I would have taken the Olds. And given same level of TLC, that Olds would have lasted a long time. A friend’s father had one in the mid 1990s that looked good and drove well, at 17 years old.
Comparing these two cars is difficult. It all…depends. mainly on your personal priorities and most of all your willingness to pay for superior materials and quality as well as the much higher prestige value.
A truly objective comparison will favor the Olds,and I often recommended big GM cars back then as a better alternative to a more expensive but embarrassingly slow 240D or such. But the status value of the star was huge.
And the quality of the Benz made them genuine long-live vehicles, but that was hard to factor into the equation back then.
Ultimately, it’s apples vs. oranges.
An interesting point about Mercedes-Benz ‘engineering excellence’ is that the various US-market 280 cars were HORRIBLE performers. They guzzled fuel and couldn’t see which way a 318 powered Volare went. Their reliability and engine durability were second rate too.
The real advantage of the 300SD in the US market was that it was allowed to visibly besoil its environment while gasoline cars had emissions requirements that they struggled to meet at all. A gross-polluting European Common Market 280SE was a stronger performer, so there was no need for an ECM 300SD. It took bureaucratic meddling to get Europeans to ruin their own air with diesels.
The real advantage of the 300SD in the US market was that it was allowed to visibly besoil its environment while gasoline cars had emissions requirements that they struggled to meet at all.
Keep in mind that these diesels did meet US emission standards of the time, as in HC, CO and NOX. There were no particulate standards of the time. Diesels inherently emit low HC and CO; eventually the much tightened NOX standards is what tripped up the diesels, as that’s hard to reduce in them.
That is a good point about the emissions rules being written in a way that was only punitive to gasoline engines, thereby encouraging the use of something that caused more harm to human lungs. There are very real reasons for not jumping on the EV bandwagon today, but people with a financial interest in the harm that will be done want EVs to be the next step to putting the middle class genie back in the serfdom bottle. Michael Moore produced a movie about it called “Planet of the Humans.” The people looking to profiteer off of renewable energy schemes are angry, because they want to make a pile of money before reaching admitting his conclusion, which is that ‘environmentalists’ are really just misanthropes who want less people.
Perhaps the “Standard of the World” should have picked up the diesel baton instead. I’m sure it would have worked out much better.
The R&T data box quotes the curb weight of the 300SD at 3885 lbs. I’m not sure why it’s 180 lbs more than the factory says.
I don’t know. I assume a/c was still optional. Their tester did have $1500 in options.
In any case, even then it’s not nearly 700 lbs. A bit less than 400.
No standard. All NA Nerve had the infamous Chrysler designed climate control a/c. Euro models made do with the better manual one. Rare.
I had a 1980 300SD what a champ. I would totally have it again as a daily. A/C was prone to problems in it
One of only three Mercedes I’ve driven, though it was a later W126 version, and the only one that was a diesel or an automatic. Wow, 35 years since I’ve been behind the three-pointed star on a steering wheel!
“Of course, Mercedes had a major head start in passenger car diesels, having built them since the 1920s.”
Um, no. The world’s first passenger diesel car, Citroën Rosalie 11UD Familiale, was introduced in 1933. Mercedes-Benz didn’t have one until 1936 when its 260 D (W 138) went on sale.
I slipped on that; corrected now.
Heck, Olds should have just tacked on a turbo. That would have solved everything. 😉
Imagine if GM had put the effort into taking one of the numerous V6s they pushed out during the gas crisis and truly put their engineering prowess into a turbo version?
Could have been superb. The engineering talent was sure available, just misused.
Olds had a turbo gas engine in the early 1960’s. Those engineers were probably retired by the time GM really needed them.
You really don’t like the GM Diesel, do you?
The diesel’s cost over the 350 or even a 307 should have made it hard to accept the $700 upcharge.
I don’t remember seeing many of diesel GM car because Canadians didn’t think to 30% higher price.
And by 1981, the motor was good but maybe not superb. It was made for a turbo and this would have made it a world leader. Instead of keeping on, GM just (yet again) threw in the towel
I’m not saying it was good or bad. I’m just referring to there being 4 or 5 postings about how terrible it was since yesterday.
I never understood the cachet of Mercedes-Benz until I bought a neighbors 79 300SD for $200.00. 400K miles. So solid I enjoyed driving it more than my 91 Fleetwood and 77 Eldorado I had at the time. The goodness of the chassis and engine was still there after all those years and mileage! Followed that beater up with a 123 wagon and a 211 CDI. Sadly I doubt anything after the 123/126 was quite as durable. Long live the last remaining 116s!
Mercedes’ are as durable as ever. My MB E320 W211 has clocked about 400.000 KM and without issues. Except from electronic stuff. It’s not a Diesel of course, as I don’t like Diesel.
But however, I think we tend to forget how mucho mucho much we use cars today on a daily basis.
In my 42 years I’ve known one guy who was an “Olds Diesel Enthusiast” and would scour barns and car auctions for full-size Oldsmobiles that still had their 350 Diesel. He would do the upgrades from the later cars etc.
However anytime I see someone with a MB turbo diesel from the 70s into the 80s they generally report they wouldn’t part with it for love nor money.
I loved the 2.7L 5 cylinder in the Sprinter van I drove for work. Just awesome powertrain. Rest of the van was a tinny, electrical gremlin (go figure) prone, uncomfortable POS. I don’t how Mike and Frank on American Pickers could stand driving one all over the country.
Been replaced by Ford Transit full-size vans. (And they have an E-series as a backup.)
Turbocharged diesels had been a feature in heavy trucks for more than 20 years when Mercedes built this transferring some truck tech into a car wasnt difficult, why GM could not dot it is the eternal mystery, but yes German Mercedes and French Peugeot and Citroen had been building diesel cars for quite some time, they still do we get them here my own car can happily sustain 170kmh with extra left, but my licence is gone if the police notice me so I dont do that often, it corners nicely at that speed too the suspension computer does its hing and lowers the ride height and tightens the spring rates and its great to drive.
Daimler-Benz may have experimented with turbocharging for their aircraft engines in the late 30’s, but all of the 600 series engines used in Luftwaffe airplanes flown during WWII had gear-driven superchargers to maintain engine power at altitude. They did experiment with a 600 Series engine with a turbocharger-the DB 625-but abandoned this effort for reasons I have not been able to determine. I suspect, from reading about their various efforts to increase power to these engines in the race with Rolls-Royce to build a faster fighter, that they ran into problems controlling the heat produced from the compression of the air-fuel mixture. This was a particular problem for fighters, which had to quickly add power and speed when engaged in battle, and to operate at widely varying altitudes and air temperatures. The problems the turbocharged Allison engine experienced when the P-38 was first used at altitude in the European theater illustrates how difficult this is to do successfully. Rolls-Royce engineers solved the problem with their two-speed/two-stage superchargers, with an air-to-liquid intercooler between the second stage and the carburetor (that would be carburettor?), that allowed the later Merlin-powered Spitfire and P-51 Mustang to triumph at bomber stream altitudes.
It helps, when you are turbocharging, to already start with a very stout system. Many 1960’s naturally aspirated John Deere 4020 Diesels were successfully turbocharged using an M & W/Rajay oil-cooled supercharger, a higher-capacity oil pan, and an upgraded radiator fan, with drawbar horsepower easily increased from 90 to 115-a 25%+ increase-with little decrease in durability or longevity to engine or transmission. You just had to resist the impulse to turn up the fuel, as you could go as high as 150 horsepower. At that point, the clutch would slip. Alternately, everything else could go bang. Less of a problem than for a P-38 at altitude over Berlin, but disheartening nonetheless.
Very interesting comments. I worked at a Mercedes dealership when the 300SD came out, at the same time I owned a 1978 Delta 88 Royale with the 350 Diesel. I actually drove that car down to the Mercedes-Benz training center in Jacksonville Florida as there was an airline strike. The head of the training center came into the classroom and asked who owned the Diesel Oldsmobile and could they do some tests on it. As far as it’s handling, it wasn’t representative of the norms for the cars, I had ordered the car with one size wider rims and tires, the F41 handling package and had installed Koni shocks when the original Delcos expired in about 2 years. While we were still in that class I heard the characteristic sound of the V8 Diesel running up on their chassis dynanmometer. I guess they got what they wanted, I got a free tank of Diesel fuel out of it.
At the dealership, I had a 300SD come it that had hit a cow up in the Blue Ridge Mountains, the radiator was destroyed, turbo cooked from being run with insuficient oil. She was in a no phone service area and no nearby town or even a gas station, she was trying to reach civilization before it quit. Engine wasn’t hurt, turbocharger was destroyed. New one was ordered, it arrived in a nice box with Mercedes-Benz labels, I opened it to find another inside it with Garret Aur Research on it.
I also onwed the turbocharged Oldsmobile, a 1963 Jetfire, 215ci Aluminum V8, rated 215HP, general consensus was “more like 300HP”. It waas saddled with one of GM’s worst automatic transmissions, Roto-Hydramatic model 5. Car was loaded, AC,power windows, power seat, only thing lacking was the AM-FM radio.
These were fast but not quick.
I also know of one where the left rear power window quit working. The reason was that somebody at Stuttgart who might have had a few too many brews for lunch had installed a motor meant for the right side. The motors mounted identically but the difference was a weep hole to let condensed moisture drain out. Put the wrong side motor in, and instead of draining, it fills up with condensed water and rusts into an inanimate lump. Which costs a lot at the parts counter.
A coworker of mine bought a used 300SD at an auction for what he thought was a bargain price. As he purchased it out of province it needed to be inspected before he could register it. He got a phone call from the mechanic doing the inspection informing him that he had bought three cars. Apparently it had been cobbled together from at least three wrecks. Several hundred dollars later it was declared safe to use and he began to enjoy his purchase, but not for long. Over the next few months he had to deal with multiple oil leaks, a failed transmission, a failed air conditioner and finally the sun roof jammed in the open position. It was so unreliable that he hung on to his Plymouth Sundance so he could get to work when the Mercedes was in the shop. I told him he should have bought a Ford Tempo.
In a way, what good was the Mercedes if it cost 3 times the Oldsmobile, and people couldn’t afford to buy it? A parallel situation to today, with new electric cars being so expensive, that only the rich can buy them.
It cost 3 times more than the Oldsmobile because it was 3 times better (at least the diesel versions).
I’m not a w116 fan but they’re incredible cars, then and now .
These early ones have the 5 cylinder engine as the later ones but without any E.G.R. nonsense, they pop up in salvage yards often and the non E.G.R. manifolds will bolt up to your later model W123….
The cars were HUGE and heavy yet they actually did corner like a sports car .
The single most expen$ive car you will ever own is a cheap Mercedes .
I still have two and love them dearly, the W123 not this W116.
Buying the Chrysler ‘Air-Temp II’ system was a serious mi$take ~ once it got ten years old it became a money pit if incredibly cold AC once you fixed it all .
-Nate