Looking for improved fuel efficiency in a Honda Insight? Consider installing a small Kubota turbodiesel engine.

      Robot Cantina via YouTube

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      To enhance fuel efficiency, automakers implement various technologies, from cylinder deactivation to active grille shutters. But what if the solution is more straightforward? YouTuber Robot Cantina installed a compact diesel engine in a first-generation Honda Insight and took it for a drive to assess fuel economy. While the Insight was among the most fuel-efficient cars available in the 2000s, the diesel swap provides even greater efficiency.

      In its original configuration, the Insight is equipped with a gasoline-electric hybrid powertrain featuring a 1.0-liter three-cylinder engine. It produces 73 horsepower and 79 lb-ft of torque, which may seem modest, but remember that the lightweight hatchback weighs approximately 2,000 pounds. Its fuel economy was remarkable at launch, achieving 53 mpg combined (48/59 mpg city/highway), as reported by the EPA.

      However, the Insight being modified by Robot Cantina is far from stock. Previously powered by a single-cylinder, 212cc Predator engine, it now boasts a three-cylinder, 719cc Kubota diesel that generates 20 hp in its standard form. This engine is typically found in small yard tractors, among other uses. The three-cylinder engine is equipped with a turbo and paired with a five-speed manual transmission sourced from Saturn.

      Robot Cantina gauged fuel economy by emptying the fuel tank, weighing the amount of diesel, refilling the tank, driving the car, and then draining and weighing the remaining fuel again. At the start of the test, the Insight held about 12.8 kilograms (around 28.2 pounds) of diesel, and by the end, approximately 2.8 kilograms (about 6.1 pounds) had been consumed. By converting pounds to gallons and considering the distance traveled, the impact of the diesel engine swap on fuel efficiency can be calculated.

      The modified Insight achieved a remarkable 70.1 mpg, significantly surpassing the official EPA figures and outperforming most new vehicles. For comparison, Robot Cantina conducted the same test with a stock Insight and recorded 62.7 mpg. He also mentions that an earlier Insight-based project, which used a supercharged diesel engine, holds the fuel economy record with a surprising 78.6 mpg. While turbochargers utilize exhaust gases as waste energy for boosting, superchargers draw power from the engine, leading one to assume that the latter might reduce efficiency.

      Robot Cantina is not finished experimenting with his Insight. He plans to test a turbocharger from a Volkswagen Lupo, a turbo from a Smart ForTwo, or perhaps both. In the meantime, he has demonstrated what many Europeans discovered years ago: compact diesel engines can deliver excellent fuel economy.

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