The eternal question: turbo or NA?
Every used car buyer faces this dilemma. Turbo engines promise more power from smaller displacement — better performance and fuel economy. Naturally aspirated (NA) engines promise simplicity and longevity. But which actually lasts longer?
We analysed reliability data from 265 engines in the EngineScope database to find out.
The numbers don't lie
Looking at the top-scoring engines in each category, a pattern emerges:
Top 10 naturally aspirated engines
| Engine | Brand | Score | Verdict |
|---|---|---|---|
| M50/M52 2.5-2.8 I6 | BMW | 95/100 | BEST |
| M54 2.2-3.0 I6 | BMW | 93/100 | BEST |
| 1NZ-FE 1.5 I4 | Toyota | 92/100 | BEST |
| M112/M113 V6/V8 | Mercedes | 92/100 | BEST |
| 2GR-FE 3.5 V6 | Toyota | 90/100 | BEST |
| N52 2.5-3.0 I6 | BMW | 90/100 | BEST |
| 2ZR-FE 1.8 I4 | Toyota | 88/100 | BEST |
| MZR 1.6 I4 | Mazda | 88/100 | BEST |
| A25A 2.5 I4 | Toyota | 88/100 | BEST |
| Duratec 2.0 I4 | Ford | 88/100 | BEST |
Average score of top 10 NA engines: 90.4/100
Top 10 turbo engines
| Engine | Brand | Score | Verdict |
|---|---|---|---|
| B58 3.0T I6 | BMW | 93/100 | BEST |
| 2.5 TFSI I5 | Audi | 83/100 | BUY |
| K20C1 2.0T VTEC | Honda | 82/100 | BUY |
| B48 2.0T I4 | BMW | 82/100 | BUY |
| EA888 Gen 4 2.0T | VW/Audi | 82/100 | BUY |
| M256 3.0T 48V I6 | Mercedes | 80/100 | BUY |
| EA888 Gen 3 2.0T | VW/Audi | 80/100 | BUY |
| 9A2 Flat-6 TT | Porsche | 80/100 | BUY |
| EA211 1.4 TSI | VW | 78/100 | BUY |
| K14C 1.4T | Suzuki | 78/100 | BUY |
Average score of top 10 turbo engines: 81.8/100
The gap: 8.6 points
The best NA engines outscored the best turbos by nearly 9 points. More importantly, 9 out of 10 top NA engines scored BEST (85+), while only 1 out of 10 top turbos reached that level.
Why NA engines score higher
The advantage of naturally aspirated engines comes down to simplicity:
- Fewer components to fail — no turbocharger, wastegate, intercooler, or boost control
- Lower operating temperatures — turbos push exhaust gases through the turbine at 900°C+
- Less stress on internals — cylinder pressures are significantly lower without forced induction
- Simpler maintenance — no turbo oil feed lines to clog, no intercooler pipes to crack
- More forgiving of neglect — missed oil changes hurt turbos much faster
The turbo reliability trap
The worst-scoring engines in our database are almost exclusively turbocharged:
| Engine | Score | What goes wrong |
|---|---|---|
| Ford EcoBoost 1.6 | 32/100 | Coolant into cylinders, overheating |
| BMW N54 3.0T | 32/100 | Everything — injectors, wastegates, VANOS |
| EA888 Gen 1/2 2.0T | 35-38/100 | Oil consumption, plastic chain tensioner |
| PSA PureTech 1.2T | 40/100 | Wet timing belt snaps |
| Fiat TwinAir 0.9T | 45/100 | Oil consumption, MultiAir solenoid |
| PSA EP6/Prince 1.6T | 45/100 | Timing chain stretch, carbon buildup |
| VW EA111 1.4 TSI | 45/100 | Twin-charge timing chain stretch |
These engines share a common theme: downsizing gone wrong. Small displacement + high boost = high stress = early failure. The promise of "big engine performance from a small engine" often means big engine problems at small engine prices.
But the best turbos are catching up
The BMW B58 (93/100) proves that turbo engines can be as reliable as NA engines — when properly engineered. What makes the B58 different:
- Forged crankshaft and rods — built for the stress, not just surviving it
- Closed-deck block — stronger than the N55's open-deck design
- Electric wastegate — precise boost control, fewer mechanical failure points
- Oversized oil cooler — keeps temperatures manageable
Similarly, the Honda K20C1 (82/100) and the latest EA888 Gen 4 (82/100) show that manufacturers have learned from past mistakes. The key improvements:
- Metal timing chain tensioners (replacing the plastic ones that failed in Gen 1/2)
- Dual injection (port + direct) to combat carbon buildup
- Better oil management to reduce consumption
The practical guide
Buy NA if you want...
- Maximum peace of mind — fewer things to go wrong
- A high-mileage daily driver — NA engines are more forgiving at 200,000+ km
- Low maintenance costs — no turbo-specific repairs
- A used car over 10 years old — older turbo technology had more issues
Best NA picks: Toyota 2ZR-FE, BMW N52, Honda L15A, Ford Duratec 2.0, Mazda MZR 1.6
Buy turbo if you want...
- Modern performance and efficiency — 150+ hp from 1.4L
- Strong low-end torque — turbos deliver power where you actually drive
- A newer car (post-2015) — turbo reliability has improved significantly
- Tuning potential — NA engines have limited headroom
Best turbo picks: BMW B58, Honda K20C1, BMW B48, VW EA888 Gen 3/4, Suzuki K14C
Avoid these turbos regardless
- Any EcoBoost pre-2018 (coolant intrusion)
- EA888 Gen 1/2 (plastic tensioner, oil burning)
- PSA PureTech 1.2T pre-2023 (wet timing belt)
- PSA EP6/Prince 1.6T (everything)
- BMW N47 diesel (rear timing chain)
The verdict
Naturally aspirated engines are still the safer bet for used car buyers, especially on older cars or high-mileage examples. But the reliability gap is closing — the best modern turbos (B58, K20C1, EA888 Gen 3+) are genuinely reliable engines that can reach 250,000+ km without drama.
The real question isn't "turbo or NA?" — it's "which specific engine?" A well-designed turbo (B58, 93/100) will outlast a mediocre NA engine. A neglected turbo will self-destruct. And a Toyota NA engine will outlast almost everything.