The right engine can cut your running costs in half
Most people optimise for purchase price when buying a used car. The smarter optimisation is running cost — specifically, engine maintenance cost over the years you actually own the car. A car that costs €3,000 to buy but needs €1,500 in repairs in year two is a worse deal than one that costs €5,000 and runs on oil changes for a decade.
What follows is a list of engine families with the lowest realistic long-term maintenance cost — not necessarily the cheapest to buy, and not necessarily the most exciting to drive, but the ones where keeping up with basic servicing is genuinely sufficient and major repairs are rare rather than expected.
1. Toyota 1NZ-FE / 2NZ-FE (1.3–1.5L naturally aspirated)
Found in the Yaris, Corolla, Auris, and various small Toyotas from 1999 onward, the NZ-family four-cylinders are as close to maintenance-free as a production engine gets in practical terms. Timing chain (not belt), conventional port injection that keeps intake valves clean without walnut blasting, and a parts ecosystem so established that independent garages stock the consumables without ordering.
Known failures are limited to the usual age-related items: valve stem seals on higher-mileage examples, occasional VVTI actuator noise at cold start, and the standard water pump and thermostat replacements. None of these are expensive. High mileage examples — 250,000 to 350,000 km — are not unusual on well-maintained cars, and engine rebuilds at those mileages are considered optional rather than necessary.
Oil change, spark plugs, air filter. That is genuinely most of what this engine needs.
2. Honda D-series / R-series (1.2–2.0L naturally aspirated, 1996–2015)
Honda's small naturally aspirated four-cylinders have powered Civic, Jazz, CRV, and Accord variants across multiple decades, and the pattern is consistent: engines that reward regular oil changes with longevity well beyond what premium brands can match. The R18 and R20 series that appeared from 2006 onward are particularly clean — timing chain, VTEC in the upper rev range for efficiency, and parts costs that reflect mass production in high volumes.
The main maintenance item is the timing belt on earlier D-series engines — replacement every 100,000 km is essential, and missed intervals can cause catastrophic damage. R-series engines use a chain and don't have this requirement. Cooling system components — water pump, thermostat housing — are the most common service items at higher mileage on both families, and Honda's parts are reasonably priced.
3. Mazda Skyactiv-G 2.0 / 2.5 naturally aspirated (2012–present)
Mazda's Skyactiv engines were designed around high compression ratios (13:1 to 14:1 in naturally aspirated form) achieved through careful combustion chamber geometry rather than additional complexity. The result is an engine that's genuinely efficient without turbocharging, with fewer forced-induction-specific failure points.
The naturally aspirated Skyactiv-G uses a timing chain, runs clean, and has accumulated very good real-world reliability data across Mazda3, Mazda6, and CX-5 applications. Known issues are minor: some carbon build-up on intake valves as a consequence of direct injection (an occasional walnut blasting is sensible preventive maintenance past 100,000 km), and the usual coolant and spark plug intervals.
iSeeCars reliability data consistently places the CX-5 with this engine among the top crossovers for likelihood of reaching 200,000+ km, which is a reasonable proxy for engine durability in daily use.
4. Toyota 1ZZ-FE / 2ZZ-GE (1.6–1.8L, 2000–2008)
The ZZ-series engines powered the Corolla, Celica, and Matrix through the early-to-mid 2000s and built a reliability reputation that holds up well despite their age. The 1ZZ-FE in particular — naturally aspirated, conservative tuning, conventional port injection — is one of the easier older engines to keep running cheaply because virtually everything that wears on it is inexpensive and available everywhere.
The one specific known issue is worth mentioning: some early 1ZZ-FE engines had an oil consumption issue related to piston ring design, most prominent on the higher-output US-market variants. This affected a proportion of units rather than all of them, and cars where it was going to manifest have generally shown it by now at high mileage. A compression test and oil consumption check before purchase is sensible; a clean result means you have the straightforward version of this engine.
5. BMW M54 straight-six (2.2–3.0L, 2000–2006)
Listed in the premium segment specifically because it punches well below its class in terms of maintenance cost when compared with turbocharged alternatives of similar performance. The M54 — found in E46 3 Series, E39 5 Series, Z4, and early X3/X5 — is naturally aspirated, mechanically relatively simple by BMW standards, and genuinely long-lived with proper servicing.
Maintenance items are predictable and finite: cooling system refresh (water pump, thermostat housing, expansion tank — do these together rather than one at a time), VANOS solenoid and seals, and valve cover gasket on higher-mileage examples. The DISA valve (intake manifold runner) is a £100–150 part that occasionally sticks and causes low-rev hesitation.
None of these are cheap in isolation, but they're predictable, they don't cascade into engine damage if caught at normal service intervals, and the specialist knowledge around the M54 is so widespread that independent shops work on them cheaply and well.
6. Volkswagen 1.6 MPI / 2.0 MPI (naturally aspirated, 1998–2015)
The unglamorous choice that consistently outperforms expectations. The naturally aspirated MPI engines (port injection, no turbo) that VW fitted to base-spec Golfs, Passats, and Škodas are simple, durable, and cheap to service. No DSG complexity, no timing chain tensioner drama, no DPF to clog — just a conventional engine doing conventional things.
These engines don't attract enthusiast attention because they're not interesting. They also don't attract big repair bills because nothing about them is complicated. Parts are shared across millions of vehicles in the VW Group ecosystem, which keeps prices competitive. A 2.0 MPI Golf with a documented service history is one of the most cost-predictable used cars available.
The timing belt requires replacement on schedule — missed intervals are the main risk. Beyond that, the main maintenance items are oil, coolant, and the occasional throttle body clean.
7. Ford Duratec 1.6 / 2.0 naturally aspirated (2001–2012)
Ford's Duratec four-cylinders powered the Focus, Mondeo, C-Max, and various other models across Europe and are unremarkable in the best possible sense. Naturally aspirated, timing belt (not chain — replace on schedule), and a parts network so well established that independent garages stock Duratec components without special ordering.
Common maintenance items are limited: the water pump is typically replaced with the timing belt as a precaution (they share the belt drive and labour costs overlap), the cam cover gasket leaks on higher-mileage examples, and the idle control valve occasionally gums up. None of these are expensive, and the Duratec is one of the engines that independent mechanics will quote confidently without needing to look anything up.
8. Honda K-series (2.0–2.4L, 2001–present)
The K-series is the engine powering the Civic Type R, CR-V, Accord, and various other Hondas, and while it has a performance reputation from its K20 applications, the mass-market K24 and K20A8 variants in regular trim are as cost-effective to maintain as any engine Honda has built.
Timing chain, conventional construction, and Honda's typically tight manufacturing tolerances combine to produce an engine where high mileage is common and unexpected failures are not. The K-series is one of the few engines that is simultaneously liked by enthusiasts (who tune it) and insurance actuaries (who have a decade of data showing it doesn't break expensively).
9. Toyota 2GR-FE V6 (3.5L naturally aspirated, 2005–present)
The 2GR-FE is Toyota's 3.5-litre V6 and has powered everything from the Camry to the Highlander to the Lexus RX. It's included here not because V6s are typically cheap to maintain — they aren't — but because the 2GR-FE specifically has a documented track record of reaching 300,000+ km without major engine work, which makes the slightly higher service cost worthwhile over the long period.
Known issues are limited: the timing chain (this generation uses a chain) requires attention past 200,000 km on high-mileage examples, and the VVT-i system needs clean oil to operate correctly — regular oil changes are more important on this engine than on a simpler design. Beyond that, the 2GR-FE reliably outlasts most competing engines from the same era.
10. Suzuki / Fiat 1.3 Multijet diesel (2003–2015)
A specific diesel inclusion because the 1.3 Multijet — developed by Fiat and shared across Suzuki, Opel/Vauxhall, and Alfa Romeo applications — is unusual in being a small diesel with a genuinely low-drama maintenance record. It lacks the DPF that turned the same era's larger diesel engines into urban short-trip problems because it was fitted without one to lower-emission-target models in some markets, and the chain-driven camshaft arrangement is simpler than many contemporaries.
Parts costs are low, independent garages are familiar with it, and the engine tends to accumulate mileage quietly. The main caveat is specific to cars used primarily for short urban trips — any small diesel benefits from an occasional longer, sustained run — but within normal mixed-use driving, the 1.3 Multijet is one of the diesel options that doesn't generate the expensive surprise bills associated with larger DPF-equipped competitors.
What these engines have in common
None of them are turbocharged (except the K-series in performance trim, which isn't the application listed). None of them have direct injection as the sole fuelling system without a secondary mitigation. All of them have parts available from multiple suppliers at competitive prices. And all of them have large enough production volumes that independent mechanics know them intimately rather than having to research them.
Complexity is the enemy of low running cost. The simplest engine that meets your power needs is almost always the cheapest engine to maintain.
Frequently asked questions
Does a naturally aspirated engine always cost less to maintain than a turbocharged one?
Not always, but the probability is higher. A turbocharger adds a component with its own maintenance requirements and failure modes. Simple naturally aspirated engines have fewer things that can go wrong expensively.
Are older high-mileage engines from this list worth buying?
With documented service history, yes. A 200,000 km Toyota 1NZ-FE with a known history is a better buy than a 100,000 km engine with no documentation, because the 1NZ-FE at that mileage with a clean record has already proven it won't fail in the way troubled engines usually do.