A Look At The 5.7L Diesel V8 Engine That Powered The Chevrolet Monte Carlo

The Chevrolet Monte Carlo is a classic, perhaps best known as the car featured in "Training Day," a film starring Denzel Washington and Ethan Hawke — but it had a very rough road in the 1980s. The fourth-gen Monte Carlo gave buyers the pick of a 5.7L V8 diesel engine, better known as the Oldsmobile Diesel. In production from 1978 to 1985, this engine was plagued with problems over its entire lifetime, and it led to a steep decline in diesel engine sales.

It's difficult to explain just how disastrous this engine was, and it seemed like whatever could go wrong did go wrong. Darrel Sand, a former developer of the engine, warned General Motors there were problems before it was released.

”In test after test, we had broken crank shafts, broken blocks, leaking head gaskets and fuel pump problems,” he said in an 1983 interview with the New York Times. ”The diesel couldn't hold up, it was a hastily converted gasoline engine with a fuel pump designed for heavy trucks.”

Instead of fixing the problems, Sand said he was forced into an early retirement. Class-action lawsuits were filed all across the United States over the issues, and the engine was even banned from being sold in California in 1979 and 1980.

There's not a single factor that made this engine a disaster, but some of the problems loom larger than the others. Perhaps the biggest issue was it was a converted gasoline engine that used a lot of the same design, so the higher compression ratio with diesel led to all sorts of issues. Using the same head bolts proved to be a huge oversight, as they stretched out and broke, and that led into head-gasket problems. From there, coolant leaked into the engine cylinders and led to failure.

The underappreciated Monte Carlo suffered as a result of this botched engine, and sales declined throughout the 1980s as a result. Even when GM moved away from the V8 diesel and replaced it with a V6, sales of the Monte Carlo struggled to bounce back. Production ended for the line as a whole in 1988 before eventually returning for the 1995 model year with a 3.1L or 3.4L V6 engine depending on the trim.

In 1982, Connecticut became the first state to pass a vehicle Lemon Law, a law that applies to vehicles under two years old or under 24,000 miles that allows you to get a refund or replacement if it's defective. Eventually, all 50 states enacted their own variation of the law to help prevent something like the infamous 5.7L diesel engine from terrorizing the public again. While this engine did a lot of damage to the public perception of diesel engines overall, it didn't stop automakers from coming up with reliable diesel engines – albeit many of them being for trucks.

The class action lawsuits of the time refunded up to 80% of the cost of a replacement engine, so owners weren't footing the entire bill once their engine failed. While it didn't do much to turn around the public perception, the V6 diesel that replaced the problematic V8 ended up being one of the best engines ever put in an Oldsmobile. Unfortunately, it was too little, too late.