I’d just finished shooting photos of my friend’s car for this story, and she was about to take me home. She turned the key to the accessory position, but the glow plug light refused to illuminate. She looked at the dash, then at me, with amusement. She gave the plugs a moment to wake, but they refused. When she cranked the ignition, the starter spun but the massive V-8 stayed silent. She popped the trunk and started to dig around for tools, and I let my boss know I’d be late returning to work—the car I was reviewing had died.
This was just par for the course for the worst American car ever built.
Richard Nixon's America
The 1970s were a difficult decade for the Big Three. In 1970, the newly-created EPA was tasked with lowering air pollution. It enacted strict new emissions laws and mandated a switch to unleaded gasoline. Automakers had just five years to comply.
As manufacturers scrambled to meet the new restrictions, the 1973 OPEC embargo sent oil prices skyrocketing 300 percent virtually overnight. In 1975, Corporate Average Fuel Economy (CAFE) laws were passed, establishing legal mandates for higher overall fuel economy among carmakers’ entire lineups. Now consumers and legislators demanded more fuel-efficient vehicles, which foreign manufacturers produced and domestic automakers largely did not.
This tumult produced the Malaise Era. Horsepower dropped across the board, as manufacturers decreased compression ratios to run engines on lower-octane gas without lead additives. Catalytic converters and complicated emissions systems siphoned off more power, without increasing efficiency. Vehicle design stagnated as engineering hours were spent on modifying existing engines to meet the new rules, rather than updating vehicle platforms to contend with stiff Japanese and German competition.
General Motors’ strategy to contend with the mire of the era was to develop an entirely new diesel motor… out of a gas V-8 design.
"GM Is Not In The Business Of Making Cars…"
GM’s "new" motor was the Oldsmobile Diesel. Instead of developing a more-compact, fuel-efficient engine—as many foreign manufacturers had—General Motors took its existing gasoline-powered Oldsmobile 5.7-liter V8 and converted it to run on diesel. Diesel engines weren’t subject to the same emissions or CAFE regulations, so the conversion allowed GM to sidestep the EPA’s new rules. Diesel fuel was also much cheaper in the 1970s than gasoline, which meant consumers cared less about poor mileage.
The Oldsmobile Diesel hit the market in 1978 after five fast-paced years of research and development, with as few changes to the existing gasoline design as possible (the most notable change was a much more robust block, to handle the high pressures of diesel combustion). At first, it was a success. It boasted moderately improved fuel economy—around 21 MPG combined, versus 15 MPG for gasoline models—and initially, sales were strong, despite the fact the diesel option was an $800 upcharge (roughly 10% of the average Olds sedan cost at the time).
From there, it all went downhill.
"...It’s In The Business Of Making Money"
The extremely rushed launch of the Olds diesel meant it was no show-stopping motor. First off, it was laughably underpowered. The iron-block, iron-head 350-cubic-inch V-8 made just 120 horsepower at launch. In 1981, four years after its introduction, the motor was detuned to 105 horsepower. This would have been less of a problem…
…if the cars it was tasked with moving had been light. Instead, the diesel V-8 was installed into Oldsmobile’s full-size body-on-frame sedans (as well as the rest of the Olds lineup and several Cadillacs). To make matters worse, most Oldsmobile diesels were paired to a THM 200 automatic transmission, a lazy three-speed without a locking torque converter.
The Oldsmobile Delta 88 I drove for this story weighs around 3,600 pounds. As an ‘81 model, it was detuned to 105 horsepower. It can do a 0-60 pull in about 20 seconds; On some steep Seattle hills, it refused to accelerate above 25 MPH, even with just one passenger and an empty trunk. Top speed, if you can reach it, is somewhere around 75 mph. Like most 1970s diesels, it exhales visible soot from the exhaust pipe and clatters like silverware in a washing machine at idle. The three-speed shifts relatively smoothly, but the massive gap in gear ratios exacerbates the already-slow nature of the car.
Bad Deals! Cars That Break Down!
GM’s corner-cutting wasn’t just bad for performance; It led to dozens of common, severe issues. The diesel 350 used the same torque-to-yield head bolts as the gas motor. While this was plenty for the low-compression gasoline engine, the high-pressure diesel motor quickly stretched or outright broke its head bolts. This caused head gasket failures. In a diesel motor, a head gasket failure is easily catastrophic, as the extremely tight clearances needed for diesel combustion create perfect conditions for hydrolocking.
When the motor first launched, cost-cutting dictated it was sold without a water separator. Diesel fuel in America in the 70s was generally low-quality, and even a small amount of water would quickly cause the high-pressure, low-tolerance injectors to rust and fail. This extremely cheap decision would frequently cost owners their motors (until a water separator was finally added in ‘81). Many buyers, in turn, used “dry gas” (a common additive from before the ethanol era) to help remove water from their fuel tanks. Unfortunately, this alcohol-based additive caused the fuel line seals to dry out and crack.
The list of problems continued: a weak and malleable timing chain would stretch, and cause the motor to run worse. The three-speed automatic transmission wasn’t capable of dealing with the torque of a diesel motor, and failures were common. Despite the higher stress on the valvetrain, GM used the same camshafts and bearings that the gas motors had, meaning anything less than perfect lubrication with fresh, diesel-rated oil would lead to failures.
The Car That Birthed The Lemon Law
The reason my test car wouldn’t start was much simpler, but still stemmed from questionable cost-cutting. The Oldsmobile diesel’s PCV was integrated into the oil cap, to minimize unique parts and cut development expenses. Soot blows directly across the top of the engine, as a result. Diesel gunk had caked onto a connector for the glow plug controller, which kept the glow plugs from heating.
Luckily, my friend knows how to fix hers, and I eventually got back to my desk. But in the 70s, when owners’ Diesel Oldsmobile V-8s inevitably failed, dealer mechanics were completely untrained on how to repair them. They would often repair the motors incorrectly, and even if they did fix it properly, nothing was done at GM to correct the underlying issues until years into the platform’s lifecycle.
This meant that failure rates on the V-8 were truly spectacular. The California EPA wouldn’t allow the Olds diesel to be sold in state for two years after its release—not because of its emissions ratings, but because every single one of the nine cars the EPA purchased had broken down before testing could be completed. There were so many class-action lawsuits regarding the engine, that by 1983, buyers had overwhelmed the Federal Trade Commission. Several states drafted the first versions of what we would now know as Lemon Laws as a direct response to the engine. Resale values of diesel-equipped cars tanked, leaving owners stuck with now-worthless vehicles, which generated further lawsuits.
By 1981, GM had fixed most of the serious problems with the V-8’s design—which is likely why my test car, an ‘81, still survives today—and launched a much-improved diesel V-6. It was too little, too late. The public soured on diesels entirely, and GM withdrew from diesel passenger cars entirely in 1985, seven years after the Oldsmobile Diesel launched.
GM sales peaked at 9.5 million cars in 1978, with the introduction of the Olds diesel. It took until 2005 for sales to top 9 million cars again.
What Did We Learn, Kids?
GM didn’t attempt another diesel passenger car until the mid-2010s, with the Chevrolet Cruze. At that time, a high-efficiency, high-mileage clean diesel was in high demand, thanks to once-again-expensive gasoline and the financial collapse of 2008. It was praised by critics for its incredible fuel economy and smooth engine.
Unfortunately, that attempt was prematurely halted by Volkswagen’s Dieselgate scandal, which ruined consumer trust in diesel engines anew, and purged the market of diesel passenger cars entirely. As we enter an era of new propulsions to meet ever-stricter emissions regulations, we can only hope that the lessons of the Oldsmobile Diesel are taken to heart.
