Will GM reconsider clean diesel in North America?

Posted By on December 4, 2008

GM swears off diesel

It’s hard to imagine General Motors going the diesel route again after their last go-around 30 years ago, but considering a number of vehicles desired by American purchasers are the larger SUV and light trucks, a clean, highly efficient diesel would make sense. Besides the fuel efficiency of a diesel engine mated to the GM Light-Hybrid drive for these larger vehicles, the diesel’s notorious long life and superior highway mileage makes them an attractive option for U.S. highways and interstates.



Olds Diesel

From the late 1970s and into the early ’80s, Oldsmobile sold the most popular car in America: the Cutlass. Olds was on a sales roll; it seemed nothing would be able to stop the division. Then came the Oldsmobile diesels, and stopping is exactly what they did best.

Instead of designing a new series of diesel engines from scratch, GM decided to base its new diesel V8 architecture on the existing gasoline Oldsmobile 5.7-liter V8’s. Of course the modifications were extensive in order to handle the 22.5:1 compression ratio of diesel operation—much stouter iron block, new cylinder heads, reinforced bottom end—but it was still a series of modifications rather than a clean-sheet design. Soon after the 5.7-liter diesel V8 debuted in Oldsmobile full-size 88 and 98 models (during 1978), the engines started tearing themselves apart.

That extreme fragility was despite the fact that the 5.7-liter diesel option cost between $800 and $1000 extra per car and only made a puny 120 hp and a stingy 220 lb-ft of peak torque at 1600 rpm. In short, these engines were awful. But the 4.3-liter version of the diesel V8 was even worse—rated at only 90 hp, it was somehow even more fragile.

The diesel V8s (and a short-lived diesel V6) were eventually offered throughout most of the Oldsmobile line and spread to the other vehicle divisions as well. And when the engines inevitably blew up, the cars they were in would either head to an early death in a junkyard or have a more reasonable powerplant swapped in.

From “Ten Cars that Damage GM’s reputation”

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  • Dave Borrelli

    If you look deeper into the corporate hierarchy at GM, you will find the true flaw in the 5.7L diesel and it’s downfall. Oldsmobile Division began development of the diesel engine in 1975. Back in those days, the divisions acted autonomously and even actively competed with each other. Oldsmobile engineers had running mules by ’76, and the prognosis was good; excellent fuel mileage, and adequate performance. However, they had durability issues. Now here comes the problem. GM’s top brass found out about the diesel prototypes, and demanded it be released immediately across all model lines (even Cadillac). Despite the Oldsmobile engineers’ objection due to the project’s incomplete state, the sales department won out over the engineering department, and the engine went into production. Meanwhile, development of the V6 continued. The V8 diesels began spilling their guts out on the highway all over the place, while the V6 reached it’s durability and reliability targets. Note that the V6 diesel did not have the durability issues that the V8 diesels did, due to their being fully developed before being sold. Later versions of the V8 were decent, but the damage had already been done. The diesel V6 suffered at the hands of the V8s reputation also. The V6, based on the 350 V8 design, was extensively modified, especially with 6 headbolts per cylinder versus 4 as on the V8. In fact, the V6 had 14 bolts holding each head down, versus the V8 with only 12 bolts. The proof that the 350 diesel could have been a reliable engine is in the fact that the V6 was, and the later versions were decent, and the Goodwrench ones (with help from Caterpillar) were even better still. A 350 diesel with ARP head bolts, Victor Reinz head gaskets, and a decent water separator will last a very long time. My ride all through high school and college was a 1981 350 diesel powered 98 Regency. It was my grandfather’s car, and it’s original engine blew up at 13,000 miles. The replacement Goodwrench engine had 150,000 miles on it when I got my license at 16, and had 260,000 miles on it when a drunk in a Dodge Ram hit me at a red light at 50 MPH (in a 35 MPH Zone) and caved in the whole back end of the car. I might still be driving it otherwise. The pitiful THM-200C transmission on the other hand was a real disaster. The only way to fix that was to replace it with a THM-350 (which I finally did after it blew up on me my senior year of high school). I loved that car. 30 MPG and it was a comfy highway cruiser and a tank.

Desultory - des-uhl-tawr-ee, -tohr-ee

  1. lacking in consistency, constancy, or visible order, disconnected; fitful: desultory conversation.
  2. digressing from or unconnected with the main subject; random: a desultory remark.