Who Makes Isuzu Diesel Engines & Are They Any Good? Here's What Drivers Say

Isuzu diesel engines have a reputation for being reliable, durable, and fuel-efficient, with a long service life. They power a wide range of vehicles, including diesel generators, commercial trucks, and rugged SUVs. These diesel engines are developed by Isuzu Motors Limited, a Japanese automobile company with a long history of diesel engine production.

Isuzu hasn't been active in the United States passenger car market since 2009, after its partnership with General Motors ended. But we remember it for being an early entrant to the sports utility vehicle party, paving the way for modern SUVs with a lineup that included the Isuzu Amigo, Ascender, Trooper, Rodeo, Axiom, and Vehicross. Still, while it ended its partnership with GM for mid-sized trucks, it continues to collaborate on commercial vehicles, such as medium-duty trucks based on the N-Series Isuzu trucks.

Isuzu diesel engines are generally regarded as reliable, particularly those running on medium-duty and commercial trucks. They are known for their durability and long service life, often exceeding 300,000 miles with good maintenance. "The engines are insanely reliable, so long as you change the timing belt. They have an iron block and an iron head. I'm a few thousand miles away from 800,000 miles, and I get 40 to 50 MPG," an Isuzu 4FB1 diesel engine owner confessed in a popular diesel forum.

Isuzu is one of the world's oldest diesel engine producers globally, as well as a pioneer in diesel technology in Japan, and has production plants in Japan (Fujisawa and Tochigi), as well as partnerships and licensed production in Thailand (with Mitsubishi), the U.S. (General Motors), and other countries. According to Isuzu, all these plants operate under strict Japanese engineering standards to ensure quality and consistency across the board. 

Isuzu has developed quite a number of impressive diesel engines, but the 4JJ1, 4HK1, and 6HK1 are the most popular among owners. The 4JJ1 is particularly known for its longevity, with owners reporting that units have run past the six-figure mark without any major issues. Let's not forget the 7.8-liter and 6.6-liter Duramax, which are actually Isuzu diesel engines in GM clothing. The Duramax 7800, in particular, is popular for its low-end torque (860 lb-ft at 1,450 RPM) and impressive durability. 

Isuzu diesel engines have quite a good reputation among diesel owners. Based on general comments from drivers, Isuzu diesel engines are known for their bulletproof reliability and routinely surpass the 300,000-mile mark with regular maintenance. While some of its diesel engines are used in passenger vehicles, particularly in Europe, the most popular Isuzu diesel engines power fleets and rugged off-road trucks. "Dad has a 2015 MU-X. Towed a massive van around the country a few times, flawless. Mate has a 2019 MU-X, had the turbo replaced under warranty, known issue, made some strange noise, otherwise, no issue. I've got a 2022 MU-X, so far, totally flawless," wrote u/BrotherBroad3698 on the r/4x4Australia subreddit.

According to Isuzu, their diesel engines have been optimized for efficiency. In their own words, "the powertrain system is cleverly designed to monitor each vehicle and how it is driven to help improve user-friendliness, and real-world fuel economy." Light trucks, such as the N-Series and Pickup variants like the D-Max, often return impressive fuel economy figures and are perfect for long hauls and fleet use. One owner, responding to a forum question about the best generation of D-Max engine and reliability, confessed that their 2010 D-Max drove better than a 2014 Toyota Hilux or a Mitsubishi Triton pickup truck — and that the throttle controller in their model year made a huge difference. 

Isuzu diesel engines are generally easy to maintain and get a lot of praise from mechanics for their simplicity in design. Some owners have also complained about common issues with specific diesel engine variants, particularly those introduced after the Diesel Particulate Filter (DPF) was implemented. "The DPF becomes a problem if you use the incorrect oil," u/Stepho_62 confessed on Reddit. He further explained that there are three other known issues with post-2016 Isuzu diesel engines: inner guard and condenser cracks, and turbocharger failure.