No diesel is not new to Mazda, however it is new to US market. They just recently started producing diesel engines and they seem very promissing on the sheet. 2.2 L twin turbo great numbers, aluminum block and components wtih 14:1 compression, starts like a gas engine (no warming up in cold) and not noisy like conventional engines. Mazda claims its as smooth as a rotary, which if you ever drove or owned you know when you drive a rotary you feel like your flying not driving.
If new 6 comes diesel, 6 speed manual and AWD I will get one hands down. The car looks sexy as heck too.