AUSTRALIAN executive car buyers have rarely had it so good, with luxury car-makers Audi, BMW, Lexus, Mercedes-Benz and Jaguar all now offering entry versions of their respective large sedans priced below $80,000.

The secret to these models are lower (though hardly poverty pack) levels of specification and downsized engines.

The BMW 520i petrol sedan tested here is priced from $77,900 plus on-road costs, which is the same as the Audi A6 2.0 TFSI and Lexus GS250 Luxury, and $2000 less than the Mercedes E200 introduced here in May.

Those buyers who prefer the torque and fuel consumption of a diesel, meanwhile, have the option of both the Jaguar XF 2.2D Luxury and Audi A6 2.0 TDI from $78,900.

The 520i is powered by the same 135kW/270Nm 2.0-litre turbocharged four-cylinder petrol used in – among others – the Z4 roadster and 3 Series sedan, matched to an eight-speed automatic transmission with Steptronic manual mode.

Such a small engine in such a big car would have been a flight of fantasy a few years ago, but a spin behind the wheel of the 520i is enough to dispel the misplaced notion that a small capacity unit doesn’t belong under such a vast bonnet.

Ever-tightening emissions regulations have driven the development of turbo technology in petrol engines to the point where such powertrains are increasingly seen as the rule rather than the exception.

For proof of this you need look no further than the excellent 2.0-litre engine fitted to the similarly sized Ford Falcon EcoBoost – what once was sacrilege now makes perfect sense.

Officially, the 520i can sprint from zero to 100km/h in 8.0 seconds, but it’s the effortless way the car generates this speed that really impresses.

All 270Nm of torque is available between 1250 and 4000rpm, meaning you get the most out of the engine at those points in the rev band where you need it. As a result, the engine is much more linear in its power delivery and feels ‘beefier’ than most downsized units of this type.

Maximum power is on tap between 5000 and 6250rpm and carries through to the cusp of redline, while the automatic transmission is programmed clever enough to hold onto gears and allow the engine to metaphorically stretch its legs, especially in Sport mode.

We seldom bothered flicking the shifter over to manual mode (without paddles) and found the eighth ratio to be superfluous on Australia’s speed-limited roads.

Such a transmission may make sense on unlimited-speed autobahns, but engaging the highest gear at 100km/h on a Melbourne freeway merely causes the 520i to shiver and shudder as though barely turning over.

Combined fuel consumption is 6.4L/100km, but after a week of mostly city driving we recorded an average of 8.2L/100km, which is still more than respectable for a car of this size.

Standard fuel-saving technology includes idle-stop, regenerative brakes that help run ancillary systems and an Eco Pro driving mode.

Further proving the versatility of this engine, a more highly tuned version can be found in the $20,000 more-expensive (and better-equipped) 528i, with power and torque increased to 180kW and 350Nm, the sprint time slashed to 6.3 seconds and official fuel use a mere 0.3L/100km higher.

Still, we’d question why you would bother, when the powertrain tested here is such a consummate performance.

Handling is typical BMW, with its quick and communicative steering among the best electric systems we’ve sampled, and its hugely capable rear-drive chassis making the big sedan feel a segment or two smaller.

Ride is composed but leans towards firm – no doubt intentionally, considering BMW’s focus on dynamics.

The standard run-flat tyres are much quieter and less intrusive at speed than previous efforts, but they are more expensive to replace and harder to source for drivers venturing beyond the city limits.

This is an autobahn cruiser in the purest sense of the term and, while this point is hard to quantify, few cars manage to feel safer and more sure-footed on long-legged cruises.

Negatives are few and start with the transmission shifter, which is confusing to operate at first, with an occasionally infuriating ‘P’ button instead of a traditional parking gear.

Rearward vision is sub-par, but – as befitting a car of this size – the cabin is large and spacious enough to comfortably sit five adults, with enough rear legroom for even your 195cm-tall correspondent and headroom to spare.

In typical BMW fashion, the front seats are on the firm side, but we found them to be comfortable and supportive enough – if not quite as sumptuous as those in the Lexus GS (or the local Holden Commodore and Ford Falcon for that matter).

Standard equipment falls short of the Lexus GS as well. It includes cruise control with braking function, front and rear sensors, dual-zone climate-control, fog lights, rain-sensing wipers, electric leather seats and seven-inch display with navigation.

And the interior fascia is not as beautifully designed as the Audi A6 – indeed, no company can match the Four Rings from Ingolstadt on that front – but it’s still well-made and functional.

On the flipside, the latest-generation of BMW’s iDrive system is appreciably better than before, making the more traditional interior controls on most other cars feel clunky in comparison.

Our biggest problems are with the generally prohibitive cost of optional extras and the fact that the outstanding head-up display from higher-specified variants is not standard, and costs an eye-watering $2800.

So, while it’s not quite perfect, we would still be hard-pressed to find a more competent and all-round excellent executive car for the money.

Cars like the 520i (and the equally affordable Audi, Lexus, Jaguar and Mercedes) are, in our view, going a long way to making their higher-specified and more-expensive siblings feel like overkill.