A lovely three-row with one expensive flaw — the turbo engine's cylinder head cracks and leaks coolant — and Mazda covers it for ten years on 2016–2020 cars, but not on 2021.

The loudest year — the head crack at its peak. 124 complaints, the largest file here, and the engine dominates it. The 2.5-liter turbo's cylinder head cracks at a stud bolt hole behind the exhaust manifold — mechanics attribute it to the weight of the turbo and exhaust hanging off the back of the head — and it leaks coolant at the back of the block near the firewall. It is frequently misdiagnosed first as a turbo coolant hose. Symptoms are a coolant smell, a slowly dropping coolant level, overheating and limp mode; untreated, it can ruin the engine. The saving grace is that 2018 sits inside Mazda's CSP11 warranty extension (ten years or 120,000 miles for this exact repair), which turns a potential walk-away into an inspect-and-confirm. Two recalls also apply, both free: a wiring-harness campaign specific to 2018 cars that can disable the passenger airbag and turn signals (19V403), and a low-pressure fuel-pump recall whose cracked impeller can stall the engine (21V875).

The launch year — same crack, no recalls at all. 99 complaints, and the same cracked-cylinder-head coolant leak is the whole story; one owner was quoted about $6,300 by a dealer. This year sits comfortably inside the CSP11 coverage window (2016–2020), so the questions to ask are whether the head has already been replaced and where the car sits against the ten-year, 120,000-mile ceiling. One genuinely good piece of news: the 2016 CX-9 carries no federal safety recall at all — we verified that directly with NHTSA rather than assuming it, and the Takata airbag campaigns people associate with the CX-9 name belong to the 2007–2015 first-generation car, not this one. Two smaller items: the Mazda Connect screen develops internal spider-cracks in the corners (program SSPB9 extends coverage seven years with no mileage limit), and the front brake discs are weak enough to warp under hard highway braking.

The quietest CX-9 — and the engine finally sorted. Nine complaints in the entire federal file, the smallest here, and they're diffuse — bumper, glass, driver aids — rather than one pattern. By this point the engine's early weaknesses are behind it: mechanics describe the 2.5 turbo as a very reliable engine, 'more so from 2019 plus,' pointing at the earlier cars' crankcase-ventilation design as the root of the older problems. No confirmed safety recall applies. What you give up is the CSP11 safety net, which ended with 2020 — but you're also buying the version of the engine that stopped needing it. Buy on condition, check the coolant level and its history anyway, and expect the same weak front brakes as every other year.

The final year — evergreen used stock. 12 complaints, and the last model year before the CX-90 replaced it — which means these will be the newest, lowest-mileage examples on the used market for years to come. The file is thin and diffuse: some steering and brake one-offs, a sunroof report. One non-recall program (SSPC8) addresses a remote-tuner battery drain. A single owner reported an electric power steering failure costing over $2,000, with Mazda covering half as goodwill; it's one filing, not a fleet pattern, and we're flagging it as such rather than inflating it. If you want this generation's driving character without the cracked-head era's coverage anxiety, this is the year to buy.

The turn — the engine gets better here. 51 complaints, less than half of 2018, and it's the year mechanics point to as the improvement: 'very reliable engine, more so from 2019 plus.' The head-crack pattern is tapering but not gone, and crucially 2019 is still inside the CSP11 window (2016–2020), so you keep the ten-year, 120,000-mile powertrain coverage for that repair while getting the better-behaved version of the engine. That combination — improving hardware, still-covered risk — makes it the value pick of the early cars. Two free recalls to verify: the low-pressure fuel pump (21V875) and a tire recall on a specific date code (19V770). Check the coolant level, ask whether the head was ever replaced, and confirm where the car sits in the coverage window.