Posted By RichC on December 4, 2008
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.
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.