BMW made a calculated decision to expand development of diesel engine technology a few years ago, but petrol engine technology is still on the agenda too.

The German company can foresee a future in which high-precision direct injection petrol engines could operate in markets around the world with the same sort of economy as turbodiesel engines of the same capacity.

The stumbling block for Australian consumers is the high sulphur content in our petrol.

It's known that Mercedes-Benz is working on a petrol engine with some of the operating characteristics of a diesel (more here), but more immediately, BMW is already promoting petrol engines that can develop 200kW of power and use as little as 7.0lt/100km.

Toni Andreevski of BMW Australia says "Going forward, (BMW engineers) are putting a lot more effort into petrol engines, because they're going to match and better diesel outputs and fuel consumption figures -- just by using clean fuel and high-precision direct injection with what they call lean-burn mode.

"It basically means that you need to have a de-NOx catalyst, so you need to run clean petrol, otherwise the sulphur in the petrol clogs up the catalyst.

"Pretty much everywhere now in Western Europe, they're running five or ten parts per million sulphur."

In Australia, BMW is holding out for the day when our petrol is down to 10 parts per million sulphur content. Once that happens, BMW will be able to bring in petrol-engined vehicles that are up to 20 per cent more economical than the current line-up.

...and then there's the 'mild hybrid' vehicles already available in Europe, such as the 1 Series with regenerative braking and auto engine stop/start facility.

In the meantime, diesel variants in BMW's passenger car range are taking up the cudgels for more economical and environmentally safer motoring. The latest addition to the model range is the 520d (more here), which is arriving in November.

We've had to wait a while for the new car. The previous model 520d in Europe was 10kW of power shy of the 'sweet spot' for Australian consumers.

BMW would never offer a 5 Series with a manual transmission in Australia, so any diesel engine had to be able to drive the large sedan with the same sort of 'brio' that BMW buyers had come to expect. The old engine just didn't cut the mustard.

With the new engine, the 520d is half a second faster to 100km/h than the petrol 523i. That's all down to the diesel engine's torque.

Diesels are comprising a larger component of BMW's sales in Australia. During 2006, BMW sold 3509 units of diesel-engined vehicles. That places the company roughly 1500 units ahead of Mercedes-Benz.

As you would expect, the lion's share of those sales went to the X5 3.0d (2091 units) and the X3 (510), but both the 320d and the 530d notched up over 300 units each.

BMW now sees itself as the country's number one marketer of luxury diesel cars. In the words of Andreevski, "We've taken that whole market by storm. From our perspective, our customers still want the car to feel like a BMW to drive, and that's what all our new diesels do."

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