Mazda unleashed its all-encompassing Skyactiv automotive technologies in 2010 to increase fuel economy with zero penalties to handling and performance. Although Skyactiv became increasingly known for its high-compression, direct-injected gasoline (Skyactiv-G) and diesel (Skyactiv-D) engines, the technology involves every aspect of the car and includes the transmission, an optimized and lightweight chassis, and entire vehicle platforms. The facelifted Mazda3 and CX-5 crossover were the first to be sold in the U.S. with Skyactiv technologies for the 2012 model year.
Mazda Skyactiv engines are not known for producing gargantuan power like Honda's famed B-Series lineup of motors. However, they are apparently as reliable as a Honda K-Series, which is no small feat since we once declared the K-Series in the Honda Element as arguably the best four-banger on the planet. The 2013 Mazda3 Sport and Touring models have a 2.0-liter Skyactiv gas engine under the hood, and the cars garnered higher-than-average consumer-verified reliability scores at J.D. Power. The trend continues with the fourth-gen Mazda3 Skyactiv, particularly the 2016 model, which got a 4.6 out of 5 reliability rating from consumer reviews at Kelley Blue Book.
Meanwhile, users on the r/MazdaCX30 subreddit refer to the Mazda Skyactiv-G engines and transmissions as "near-bulletproof," "very reliable," and "with little to no problems." Backing up those claims is Mazda's ascension to the third spot in the 2025 J.D. Power Vehicle Dependability Study. Furthermore, Mazda now ranks second in the mass market segment behind Buick, with Toyota falling into third place. So, yes, Mazda Skyactiv engines have proved to be solid, reliable, and relatively fuel-efficient, but it's all by design.
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Mazda likes challenging the boundaries of engineering and design. Want proof? Look no further than the legendary RX-7 FD and its sequential twin-turbocharged rotary engine. The RX-7 is legendarily fun to drive, yet it drinks oil and gas like a top-fuel dragster and is notorious for its finicky upkeep. But for Skyactiv, Mazda had to rethink the combustion engine, and it starts with an unusually high compression ratio.
Older Mazda engines typically have an 11:1 compression ratio. It essentially means that the engine requires 11 parts of air for one part of fuel to combust effectively. Mazda Skyactiv-G engines feature a 14:1 compression ratio (13:1 for vehicles in North America) to squeeze out more power from every piston stroke. The pistons are different, too, and feature a domed shape with a cavity in the top-center that enables more efficient combustion.
Meanwhile, the engines have lengthier 4-2-1 exhaust headers to reduce heat soak, and Mazda engineers utilized new pistons, rods, and roller finger followers to reduce friction. Moreover, Skyactiv engines have a forged steel crankshaft, dual variable valve timing with electronically variable intake valves, direct injection, and a 15-pound-lighter aluminum block. Combined with the related Skyactiv transmissions and chassis tuning, the Mazda3 Skyactiv received an EPA-rated 30 mpg in the city and up to 40 mpg on the highway.
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Mazda Skyactiv-G engines are fairly reliable and trouble-free when given timely maintenance. Then again, nothing is perfect, and there are some issues worth noting. For instance, the Skyactiv-G has a delicate mass airflow (MAF) sensor that's known to trigger fault codes when contaminated with dirt. In some cases, replacing the MAF sensor at around 60,000 miles is necessary to fix the problem. It affects both the 2.0-liter and 2.5-liter Skyactiv engines in the Mazda3 (2014 to 2018), Mazda6 (2014 to 2017), CX-3 (2016 to 2019), and CX-5 (2013 to 2019).
Moreover, Skyactiv engines are prone to excess carbon buildup, but it's a problem that plagues most direct-injected engines. When it comes to Mazda, the 2.0-liter and 2.5-liter Skyactiv engines require frequent cleaning and servicing of the PCV valve to avoid clogging the intake valves with power-robbing carbon deposits and to prevent oil dilution.
It's also worth knowing that certain Mazda vehicles with Skyactiv-G 2.5T engines are involved in a class-action lawsuit for engine defects related to persistent coolant leaks. The lawsuit claims that Mazda has issued a series of technical bulletins to address the issue, but that it failed to issue recalls, warn consumers, or extend the factory warranty on affected cars. The plaintiff adds that the Mazda6 (2018 to 2021), Mazda3 (2021 to 2024), CX-30 (2021 to 2024), CX-9 (2016 to 2023), CX-5 (2019 to 2024), and CX-50 (2022 to 2024) all have defective Skyactiv-G 2.5T engines.
