The Oldsmobile Diesel V6 Fixed The Brand's '80s Diesel V8 Woes, But It Was Too Late To Matter
In the early '80s General Motors sold more diesel cars than any other company in America, claiming more than half the entire market. Unfortunately, this utter dominance would nearly prove to be the ruin of diesel in the United States, because the engines GM was selling—based on an Oldsmobile design that was rushed to market and then built with the cheapest possible parts—was absolutely terrible.
After several years of endless repairs, hundreds of thousands of frustrated owners, and a general chill towards diesel outside of trucks and commercial vehicles, General Motors was out of the diesel business. It wouldn't be until Volkswagen and Mercedes-Benz got more aggressive with the fuel in the '90s and early 2000s that it would mount any kind of passenger car comeback.
Underneath that dark cloud, however, lurked one single, shining ray of light. It seems that despite its V8 woes, Oldsmobile's engineers had managed to turn out a perfectly serviceable diesel V6 engine that avoided all of the problems of its bigger brother and finally delivered on the promise of decent power and excellent efficiency. Too late to make a difference in the diesel wars, this unique six-cylinder engine has been almost forgotten by even the staunchest defenders of '80s American automotive design.
Quick, Cheap, And Disastrous
The sins of the original Oldsmobile diesel V8 were many. Forced to use the same bore and stroke as the brand's 350 cubic inch gas engine rather than working from a clean slate, the engine also lacked a water separator and featured head bolts that couldn't withstand diesel pressures. Throw in legions of owners trying their home-brewed fixes for all of the above and dealer techs forced to replace broken parts with ones that were guaranteed to fail again, and the entire mess cost hundreds of millions more in lost sales and customer ill will than it would have to simply build a better motor from the get-go.
That fact was amply illustrated by the V6 engine that Oldsmobile introduced in 1982, roughly three years after the V8 had begun its wrecking ball course through the automotive landscape. Displacing 4.3L, it was directly derived from the eight-cylinder and addressed nearly every one of the problems inherent in its ancestor. Namely, it came with an improved and balanced nodular iron crankshaft, longer main cap bolts, and a water separator. The latter kept the moisture common in diesel fuel at the time out of the combustion equation (and also prevented owners from dumping bottles of alcohol in their tanks to take care of the problem on their own, thus eroding their fuel system seals and other rubber components in the process). Also new were six head bolts in place of four for each cylinder, which represented a 50 percent improvement over the V8.
Too Late To Matter
No one else had ever built a diesel V6 outside of the truck market before, and the Oldsmobile effort was a winner. With 85hp and 165 lb-ft of torque on tap, the six-cylinder wasn't that far behind the 105 horses and 205 lb-ft produced by the V8 diesel in its later years (after GM had transplanted many of the fixes first found in the V6).
The LT6 version of the motor was offered in the G-body mid-size cars like the Buick Regal, Oldsmobile Cutlass Supreme, and the Chevy Malibu and Monte Carlo from 1982 to 1984.
A transversely-mounted version, the LT7, was installed in A-body sedans like the Buick Century and Chevrolet Celebrity (as well as the Oldsmobile Cutlass Ciera and the Pontiac 6000) from 1982 to 1985 (with a rare, 85-only LS2 edition found in larger cars like the Buick Electra and the Oldsmobile 98).
By the time GM got diesel right, it was far, far too late for it to salvage its reputation with customers. Posting an impressive 41-mpg on the highway (using that era's EPA mileage estimates) had no sway over loyal buyers who had been badly burned by the diesel V8 and wanted no part of the General's oil-burning future. The engine was quietly retired by the middle of the decade.
The A-body platform would go on to (relative) greatness, leaving its brief dalliance with diesel in the dust as it powered Chevrolet, Oldsmobile, Pontiac, and Buick through the rest of the '80s and into the early '90s. GM didn't tempt the diesel fates again until the 2014 model year with the Chevrolet Cruze, a solid performer that was itself brought down by another diesel scandal: Volkswagen's tampering with pollution controls in its own turbodiesel engines, which cast a pall over the entire market and drove most of the passenger car flock featuring these motors all the way back to their European strongholds.