The more I dig, it appears the 2018 Mazda3 did not get the CD option. Here are 3 separate write-ups, 2 of them from Mazda press releases.
Ray
NORTH AMERICAN MAZDA MODELS EQUIPPED WITH CYLINDER DEACTIVATION
This exciting new technology will be found inside the latest SKYACTIV ®-G 2.5-liter engine, which is capable of producing 187 horsepower and 186 lb-ft of torque. This engine is available on the 2018 Mazda CX-5 and the 2018 Mazda6. Being the innovators that they are, Mazda is the only automaker to offer up cylinder-deactivation technology on a four-cylinder engine in North America.
Usually, "running on all cylinders" is considered a good thing but not all the time. Sometimes, that means burning fuel when you don't need to, which is why Mazda's engineers went back to the drawing board to introduce a new cylinder-deactivation technology for 2018 that can cut down on fuel-consumption in certain operating conditions. The new cylinder-deactivation system can be found in the latest SKYACTIV-G 2.5-liter engine that delivers 187 horsepower and 186 lb-ft of torque.
Available on the 2018 Mazda CX-5 and 2018 Mazda6, Mazda is the only automaker to offer cylinder-deactivation technology on a four-cylinder engine in North America.
The Mazda3 will give you access to one engine option. This is a 2.5L I4 gasoline engine that will give you access to 185 horsepower. As a larger vehicle, the Mazda6 will give you access to a larger engine. New for the 2018 model year, the Mazda6 now offers both the 2.5L I4 engine that the Mazda3 comes equipped with and additionally offers a turbocharged engine option. This 2.5T I4 gasoline engine will give you access to 250 horsepower. Another difference between the two models is the addition of cylinder-deactivation technology to the Mazda6 lineup.
