LUXURY-CLASS diesel cars are pretty rare in Australia, but Mercedes has always felt a commitment to supplying the small market that exists anyway. The latest 2.7-litre turbo diesel offered in the updated E-class is a strong enticement to those who have not previously shown any interest in oil-fired engines because it rivals petrol engines in performance while offering traditional diesel economy. A pity that clean, fuel-conserving performance is not available at the lower end of the market. By the way - the E-class update resulted in more than 1800 changes to the car.