Monterra - its just that I feel personally many may not have a need for diesel. For example you cite 50% more torque, great. But those who drive in mostly urban flat areas with mix of city/highway with zero need of towing along with (a fact I just reviewed) - the EU diesel CX-5 doesn't seem to have too much acceleration gains in 0 to 62 is 10.3 sec. AWD! See here
Efficiency: I use non-premium gas and premium is always about .30 cents more and at today's prices it's about 10%. Coupled with diesel being even more than premium by at least an additional 10 cents I am looking at .40 cents increase which boils down to approx. 15% increase in cost vs. standard gas. I did some maths and yes - with higher MPG for diesel it comes out on top but (and a big but) out here with gasoline engines outshining diesel 1:20, # of pumps having diesel is much less and those which do have them are invariably on the costly side even for standard gasoline. In effect, that 15% increase is now 25% increase, then it makes no sense.
What I am trying to get at is Mazda might introduce the diesel but it'll be a tough sell, at least in these parts.
That's your area. Here diesel is sometimes more and sometimes less than 87 octane regular.
Just a few posts above, Robene explained the benefit of the torque in the way the car drives. It isn't about 0-60, or towing.
Better fuel economy isn't just about fuel cost, it also increases range.
I don't want to rev to 6000 RPM when I'm accelerating from a stoplight on my daily commute. I want the easy, low rpm torque that the diesel promises.