BMW’s latest X5 M and X6 M promise better performance and greater efficiency than their predecessors.

Both models are powered by a new 4.4 litre V8 petrol engine that features direct injection, twin turbochargers and variable valve timing. Producing 567 bhp (423 kW / 575 PS) with 750 Nm (553 lb/ft) of peak torque, its output is sent to all four wheels via an eight-speed automatic transmission.

As a result, the X5 M and X6 M will accelerate from rest to 62 mph (100 km/h) in 4.2 seconds before going on to an electronically-limited top speed of 155 mph (250 km/h).

The 2015 BMW X5 M...

...and the X6 M. Scroll down for more images.

Combined cycle fuel consumption and carbon dioxide emissions are 25.5 mpg (11.1 l/100km) and 258 g/km respectively. Although those figures might not appear particularly impressive in isolation, they do represent 20 percent improvements.

Numerous chassis tweaks have been introduced to make the most of the extra pace. Among them are a firmer and lower suspension set-up, recalibrated electrically-assisted power steering, 20” wheels shod with Pirelli P Zero tyres and upgraded brakes with six-piston calipers at the front. The Dynamic Performance Control and Dynamic Stability Control systems are bespoke, too.

To visually distinguish the M versions they are fitted with larger front intakes, ‘Air Breather’ vents behind the front wheels, twin-stalk door mirrors, four exhaust tailpipes and a rear diffuser. Unsurprisingly, their interior specification includes front sports seats, Merino leather upholstery, an anthracite headliner and aluminium trim pieces.

The 2015 X5 M costs £90,170 in the UK, while the X6 M has a £93,070 price tag. Deliveries are due to begin next April.