MAZDA'S five-year-old premium sports coupe has undergone a mid-cycle model upgrade, with a new top-of-the-line model called GT and a new six-speed automatic heading the long list of mostly minor revisions for the 2008 RX-8 range.

While the new model is not exactly an overweight slouch, the manual’s much shorter gearing - intended to counteract the lack of low-rpm engine torque - has only helped make the RX-8 slower in the crucial 0-100km/h sprint and increased fuel consumption by 0.3L/100km.

Despite being slower in a sprint and thirstier, Mazda claims that in new GT guise the 2008 model is quicker around a track than its predecessor.

The most obvious visual changes are at the nose of the RX-8, where bigger air intakes and larger headlights are fitted. Together with a restyled spoiler and underbody improvements, the changes result in a slightly better aerodynamic Cd figure of 0.30 (compared with 0.31 for the previous RX-8).

Side air intakes now incorporate side indicator repeaters while at the rear the mesh bumper insert from the previous model has been deleted, new tail-lights fitted and larger-diameter exhaust outlets added.

New wheels have been fitted too: the 18-inch alloys on RX-8 and RX-8 Luxury are the same size as before but feature a new design, while 19-inch alloys are fitted to the GT. A space-saver spare is used in all models.

Inside, the central section of the instrument panel has been redesigned and the centre panel employs what Mazda calls Action Illumination for more clear response to control inputs.

Front seats have smaller head restraints for better rear visibility and are contoured differently to improve support during cornering. The entry-level and GT seats use a new, more dense fabric material, while the Luxury’s leather seats use a fine-pitch perforation in their centre panels and, unlike the previous two-tone leather seats, are monotone - either red or black.

The Luxury’s electric driver’s seat has finer seat position control and a new forward folding mechanism operated by a switch on the seatback.

The Bose audio system’s amplifier on the Luxury been upgraded, and a vehicle-speed sensor added to make it easier to hear the system at higher speeds. An auxiliary input jack is also new for all RX-8s.

As before, the engine has different outputs according to the transmission used. The manual version develops 170kW at 8200rpm and 211Nm at 5500rpm, both of which are unchanged from the previous model. Mazda claims that the torque curve has been changed to improve low-to-mid range rpm response.

The manual achieves a 12.9L/100km fuel consumption figure, increased from 12.6L/100km thanks to its shorter gearing.

Mated to the new automatic, which is available only on the Luxury, the engine develops 158kW at 7500rpm and 211Nm at 5500rpm, and averages 12.1L/100km.

The engine has an electronic oil pump replacing an engine-driven hydraulic unit and a better oil spray design. New twin knock sensors are claimed to reduce the chance of pre-ignition occurring.

The six-speed manual is also new, borrowed from the MX-5 but with altered transmission ratios. The final drive has been shortened from 4.444 to 4.777:1 for better slow-speed acceleration.

The new RX-8 manual is slower in the 0-100km/h sprint (6.4 seconds versus 6.2) mostly because, as a result of the shorter gearing, a time-robbing gearshift from second to third is required.

The manual is also thirstier than the automatic version because of the shorter gearing.

The six-speed automatic offers a tiptronic-style gearshift gate or steering wheel-mounted paddle shifts. The automatic has taller gear ratios and final drive ratio than the manual.

Body changes to improve stiffness include a trapezoidal strut brace on manual models (the auto has a conventional strut brace), thicker steel for the strut towers and at the rear of the wheel apron, plus spot welds added to the hinge pillar in the door openings.

The fuel tank has increased capacity from 61 litres to 65 litres.

Suspension changes to the base and Luxury model include stiffer dampers and lengthened rear suspension links. The upper long lateral link has a raised attachment point to better control toe-out changes and thus stability during braking.

The GT has Bilstein dampers and a urethane-filled front suspension cross-member, as featured on the 40th Anniversary limited-edition version earlier this year.

The new model costs $730 more for the base model at $49,720, and $2530 extra for the Luxury.

From the base model up the RX-8 has an anti-lock braking system (ABS), electronic brake-force distribution (EBD), traction and stability control, front, side and side curtain airbags, front seatbelt pretensioners with load-limiters and anti-whiplash front seats.

The base model features list includes 18-inch alloy wheels, a torque-sensing limited-slip differential, heated/power mirrors, power windows, remote locking, climate-control air-conditioning with pollen filter, steering wheel-mounted cruise control, in-dash six-CD player, a leather steering wheel and gearshifter, driver’s seat height adjustment and four cup-holders.

In addition, the RX-8 Luxury offers leather seats, a powered glass sunroof, Xenon low-beam headlights, front foglights, a Bose 300-Watt sound system and power adjustable driver’s seat.

The RX-8 GT shares features with the base model with the exception of 19-inch alloy wheels, front and rear spoilers and side skirts, front foglights, Xenon headlights, Recaro front seats with leather/cloth facings, aluminium pedals and footrest, and a leather handbrake cover.

The RX-8 is available in Crystal White Pearl, Sunlight Silver, Velocity Red, Aurora Blue, Diamond Grey, Galaxy Grey, Sparkling Black and Brilliant Black.