There is a Japanese driver on youtube in Japan who did 500,000km on a diesel 2.2L CX-5 with the first version from 2012. He said fuel efficiency is double compared to the Toyota HiAce. Mostly highway driving which is where the diesel works best for mileage and reliability. For city driving or short daily drives, gasoline is better. Also Mazda diesel engine needs oil changes every 5000km max. In Japan diesel is taxed a lot less than petrol so it makes sense in terms of fuel costs overall
The Diesel has alot of fundamental issues..you should check out the Australian reviews of the 2.2...cracked blocks and all...they always recommend to never ever buy a Mazda diesel..just get the Na 2.5...enough power and way more reliable , also , Mazda have never mentioned that they have ironed out whatever issues they had with the diesel , the engine code still same which means its still the same one that you hear the horror stories come from
Its the 1st version back before 2018, after that the diesel cx5 is basically bullet proof with huge torque and lower FC vs the 2.5 turbo. BTW, the 2.5NA is gutless