Andrew Hamilton is deeply smitten by the diesel version of the BMW 7 Series
It's a difficult task reporting on degrees of excellence but that's what we have been faced with when writing about BMW diesels. The latest BMW diesel engines in the 7-series flagship cars are almost predictably in this sphere and last Friday on the quick-flowing autobahn network around Munich and on sleepy Bavarian country roads, we got a taste of the latest and best of Bayerische Motoren Werke.
As with petrol, there are just two models in the line-up, the 730d and the 740d, the former in six-cylinder form and the latter with a V8 unit. It's only the 730d that we will see in Ireland early next year. The 740d won't be sold in right-hand-drive here simply because it isn't going to be marketed in our neighbouring island which happens to be the only major right-hand-drive car diesel market in the world.
Power, performance and agility are flowing in abundance with both cars. The 730d has a maximum output of 218bhp at 4,000rpm, it gets from 0 to 62mph (or 100kph) in eight seconds and the top speed is 146mph. That means that it's a mere half second slower than the 735 V8 petrol car, surely an inconsequential detail.
As for the 740d, it delivers 258bhp at 4,000rpm, has a 0 to 62mph time of 7.4 seconds and a 155mph maximum speed.
Enhancing the driving pleasure of "the ultimate driving machine" is the six-speed automatic transmission that has already made its debut in the 735i and 745i petrol models. In both diesels, there's extraordinarily high gearing: at speeds above 80mph, the engine is ticking over very imperceptibly at 2,000rpm.
Could we find a tell-tale diesel clatter at any stage? Not really. In the 730d, the sound from the exhaust was more of a sporty burble, especially when accelerating on the secondary roads. It wasn't unpleasant, in fact rather endearing.
In the 740d, the overriding impression is of hush and quiet: what sound there is from under the bonnet is remote and distant. These are second-generation common-rail diesel engines and their up-to-the-minute technology offers faster and more precise injection. BMW engineers say that, instead of compressing a single squirt of fuel to the maximum pressure, the second generation system injects four times per piston cycle to produce a smoother and more efficient combustion process. Diesels at the end of the day, are about travelling longer distances using less fuel and saving money.
Buyers opting for the 730d aren't likely to be needy cases but their fuel consumption, according to BMW, should be about 30 per cent better than the petrol models - in other words about 33.2 mpg.
Diesel accounts for almost 30 per cent of all BMW car sales worldwide. Diesel has been around in previous 7-series models but we haven't seen it here in Ireland simply because they didn't appeal to BMW GB which thought it was inappropriate for the image. How times have changed!