Buying a used car has long meant focusing on engine reliability. High-profile cases, including widely publicized issues with certain engines, have reinforced this concern and even led to legal action aimed at improving compensation for repairs. Yet this focus may now be too narrow.
A study conducted by CarGarantie, based on around one million warranty contracts reaching expiry in 2025, shows that several other systems are increasingly responsible for expensive breakdowns. The data suggests a broader, more complex picture of automotive reliability.
Costly Failures Extend Beyond the Engine
The engine remains the most expensive category of damage on the used car market, though its share is declining. According to CarGarantie, it accounted for 24.2% of total compensation costs in 2025, down from 26% the previous year.
Fuel system components rank second, representing 17.2% of expenses. This category includes turbochargers, which have become essential in modern vehicles but are not designed to last indefinitely. Their replacement often exceeds €1,000 (about $1,080). Injector failures are also common, particularly on diesel engines and certain ethanol-compatible Ford units.
These figures illustrate that while the engine still dominates in absolute terms, other mechanical elements are responsible for a growing share of repair bills.
Electrical Systems Overtake Gearboxes in Repair Costs
Electrical systems now rank third among the most expensive sources of failure, rising from 12.9% to 13.6% of total costs. According to Automobile Magazine, diagnosing and repairing electrical faults can be especially complex, often leading to high labor expenses in addition to the cost of components such as wiring harnesses.
Gearboxes, although potentially very costly when a full replacement is required, fall behind in this ranking. In some cases, manufacturers partially or fully cover these repairs, which reduces the financial burden recorded by warranty providers.
The study does, however, have its limits. It does not include emissions control systems, which are frequently reported as expensive failure points in user feedback, a detail noted in the same source.
New Vehicles Show a Shift Toward Electronic and Comfort Systems
The trend is even more pronounced in newer vehicles. For the first time, electrical systems top the list of repair costs, accounting for 19.3% of compensation. Over the same period, engine-related costs declined from 18.4% to 16.9%.
Fuel systems remain in third place at 13.4%, still including turbochargers. Meanwhile, comfort electronics, particularly multimedia systems, are emerging as a significant source of costly failures. These issues are not limited to minor bugs; they can require expensive interventions.
Such systems are often excluded from extended warranty programs offered by manufacturers. Stellantis is cited as one of the few groups covering multimedia systems for up to eight years, though only under its premium brands, including DS, Lancia, and Alfa Romeo.
This evolving distribution of repair costs highlights a broader transformation in automotive technology, where complexity increasingly shifts risk away from traditional mechanical components.
