Mazda6 Maintenance
The 2016-2021 Mazda6 (third generation, “GJ/GL”) ships with one of two 2.5-liter Skyactiv-G four-cylinders, and which one you have decides most of your service routine. The naturally aspirated 2.5 (~187 hp) is in the Sport and Touring trims for the whole run. The turbocharged 2.5T (227 hp on 87 octane, 250 hp on 93, 320 lb-ft) arrives with the 2018 refresh and lives in the Grand Touring, Grand Touring Reserve, and Signature trims. Mid-grade trims got a refreshed cabin and standard i-Activsense for 2018; mechanically the two engines diverge more than the brochure suggests.
NA 2.5 vs. turbo 2.5: what actually differs
Section titled “NA 2.5 vs. turbo 2.5: what actually differs”The bottom ends share a lot of parts, but the maintenance specs do not.
| NA 2.5 (Sport/Touring) | 2.5T (GT/Reserve/Signature) | |
|---|---|---|
| Oil viscosity | 0W-20 | 5W-30 |
| Oil capacity (w/ filter) | ~4.8 qt | ~5.1 qt |
| Compression ratio | 13.0:1 | 10.5:1 |
| Fuel | 87 octane | 87 OK, 93 for rated power |
| Spark plugs | per schedule | ~40,000 mi |
The turbo runs the thicker 5W-30 and the lower compression ratio because it’s a different state of tune, not just an NA block with a snail bolted on. Mazda lists 87 octane as acceptable for the turbo, but the engine pulls timing on it; the 250 hp / 320 lb-ft figures are 93-octane numbers and you give up roughly 20 hp running regular. If you bought the turbo for the torque, feed it premium.
Both engines respond badly to stretched oil intervals. 5,000-mile changes with a full-synthetic that meets spec is the safe number, and the turbo in particular is sensitive to oil quality.
The known issue: 2.5T cylinder-head coolant leak
Section titled “The known issue: 2.5T cylinder-head coolant leak”The defining problem on this car is on the turbo engine specifically. The cylinder head can crack around the exhaust-manifold side (at a stud-bolt hole or the manifold flange) and weep coolant. Left alone it leads to coolant loss and, in the worst cases, engine failure.
Mazda has acknowledged it. Customer Service Program CSP11, matching TSB 01-002/23 (Feb 10, 2023), extends the powertrain warranty on 2018-2020 Mazda6 2.5T vehicles to 10 years / 120,000 miles for coolant leaks at the cylinder head around the exhaust manifold. Owner notifications went out by mail starting November 2024, and the program reimburses prior out-of-pocket repairs for the same condition. If you own one of these, check your coolant level and the area around the exhaust manifold for staining, and confirm whether your VIN is covered before paying for the repair yourself.
The NA 2.5 does not carry this extension. Some turbo cars also show elevated oil consumption in early miles, tracked under a separate TSB; watch your oil level between changes rather than assuming the dash will warn you in time.
Routine items
Section titled “Routine items”Nothing on the Mazda6 is exotic here — brake fluid, cabin/engine air filters, and the transmission follow the standard Mazda intervals in the owner’s manual’s maintenance schedule. The turbo’s only extra recurring line item beyond the NA car is the 5W-30 oil and the ~40k spark plugs.
Infotainment and CarPlay
Section titled “Infotainment and CarPlay”The 2016-2021 Mazda6 uses the Gen 6 Mazda Connect head unit, so its screen behavior, factory CarPlay timing, and the touchscreen quirks are covered on the dedicated Mazda6 CarPlay and common complaints pages rather than here. These cars run the same CMU we support; see supported vehicles for the firmware line.