So far Mazda has taken a somewhat unconventional route to improving fuel efficiency of its vehicle fleet, focusing on lighter materials and new designs instead of rebuilding its powertrain lineup. It has done the company well, but to move to the next level of efficiency the carmaker is also planning on upgrading its engine and transmission lineup.

By a 2015 deadline Mazda wants to have all of its petrol engines running direct-injection and stop-start technology, reports Automotive News. Continued weight-loss is also on the docket, however, with each platform planned to go on a 220lb (100kg) diet by the next iteration. The upgrades will take place in stages over the coming years, with the early focus on the smaller cars in the lineup. The changes will also reflect a greater degree of freedom and reduced control by parent company Ford, though continued sourcing of parts and pieces from the company parts bin is likely.

The Mazda2, for example, will get an all-new (to America, at least) four-cylinder engine provided it passes U.S. testing. The plan is to bring the small car to market by 2011. The Mazda3 is getting a complete redesign, coming early next year as a 2010 model, offering two different engines as it does now, though details on the exact specifications are still lacking.

The newly reworked U.S.-market Mazda6 gets unique engines that will stay the same for the near future, with a 2.5L four-cylinder rated for 170hp and a 3.7L V6 good for 272hp. The sedan is the only model available now, as the hatchback and wagon have been discontinued.

Exciting developments could come toward the far end of the 2015 deadline as the pushed-back MX-5 Miata redesign is expected to happen in 2012 and a coupe version, possibly based on the Kabura concept, could be in the works as well. Sports car enthusiasts will no doubt be awaiting the new model eagerly, as it is still, even after two decades of sales, one of the best performance and handling bargains in its class, with an eye toward efficiency that most of its competitors lack. The RX8’s full redesign is equally far off, though planned increases in displacement and improvements in fuel economy are already being promised.

The company’s SUVs and MPVs will see recalibrated automatic transmissions, mild redesigns around 2010 and 2011 and possibly the introduction of a non-turbo version of the CX-7 to reduce fuel consumption, though the concordant drop in performance may leave some buyers dissatisfied. The CX-5 previewed by the Kazamai Concept (pictured) shown at the Moscow Motor Show and sharing Ford Kuga underpinnings isn’t expected until 2010 as a 2011 model. The Tribute, essentially a Mazda-badged version of the Ford escape, will likely be axed as the CX-5 moves into the lineup.