Does the Innova’s Engine Really Last? Failure and Survival of Toyota’s Nine D-4D Diesels in British MOT Records

Toyota’s 2.5-litre 2KD-FTV diesel, the engine of the first-generation Toyota Innova in India, has a reputation for running for hundreds of thousands of kilometres. The same engine was sold in Britain in the Hilux pickup and the HiAce van, alongside eight other Toyota-designed engines carrying the D-4D name. This study asks whether the reputation belongs to the whole family or to a few of its members, using about 119 million British MOT roadworthiness test records from 2015, 2019 and 2023. Each engine was identified from its recorded capacity and year of first use and compared with the rest of the British diesel fleet, with rival pickups and vans, and with petrol versions of the same Toyota cars, always inside cells of the same vehicle class, age and mileage. The hypotheses were written down before any comparison was run. In 2023 eight of the nine engines failed the MOT less often than comparable diesels and the ninth no more often, but only five by a material margin (odds ratios 0.368 to 0.882); the 2KD’s margin was small (0.954), and the engines differed far more than chance allows (I-squared 0.983). Where the 2KD stood apart was in staying on the road: vehicles with it that were tested in 2015 were 33 percent more likely than comparable diesels to be tested again in 2023 (risk ratio 1.331), the highest figure in the family. Against vehicles built for the same work the picture narrows. The HiAce failed less often than rival vans (0.615), while the Hilux with the 2KD failed slightly more often than rival pickups (1.055) though with far fewer engine-and-emissions failures in 2023 (0.639). Toyota’s car diesels held no material advantage over their petrol twins on the test as a whole, though the 1CD and 1ND had materially fewer engineand-emissions failures. A positive control built on a documented Toyota bulletin for the AD engines worked only in part: the fault showed in survival but not in the MOT’s engine section. Raw failure rates pointed the wrong way in 10 of 25 engine comparisons, a Simpson’s paradox created by the D-4D fleet’s greater age and mileage. The reputation survives as endurance under heavy use, not as a family-wide freedom from faults.