I've fallen in love... with an engine! After 14,000 miles, the latest generation twin-turbo diesel of our BMW 535d has proved itself to be a genuine masterpiece.

The 3.0-litre unit's 282bhp and 560Nm of torque ensure this large executive estate has the firepower to see off a 3.2-litre Audi TT.

But the best bit is the economy we've been getting. It's rarely less than 32mpg and, on a couple of occasions, returns have risen tantalisingly close to 40mpg.

What's more, the on-board diagnostics are still telling us it doesn't need servicing for another 5,000 miles (although the oil is starting to look a bit thick). It's not flawless, of course - the six-cylinder unit is gruff when cold and isn't as tuneful as a petrol. Still, the benefits of BMW's Efficient Dynamics programme outweigh any such criticisms. The hi-tech alternator recharges the battery via the brakes, sapping less engine power.

It proved its worth during a recent family holiday to France. The Touring effortlessly swallowed four of us, plus luggage (including three bikes on a Thule towbar rack), then made mincemeat of 2,000 motorway miles, averaging 32.3mpg and costing £233 in fuel.

My only complaint is that the 535d is too luxurious to be used for rugged family duties. I simply couldn't bring myself to fill the beautifully carpeted boot with a collection of sandy buckets and wet towels.

Yet the 5-Series nearly didn't make it to the Continent at all. A week before we left, the iDrive screen informed me that the speed-sensitive steering had packed up, making the car heavy to manoeuvre in town, but oddly light and nervous on the motorway. The driver's electric window also gave up the ghost.

A call to BMW's Emergency Service had assistance on the scene within 45 minutes. However, the engineer's computer wasn't up-to-date enough to ‘talk' to my car, so it had to go to a dealership to be fixed. A courtesy vehicle was provided and, although I had to do some running around myself, it was all sorted within 24 hours.

The experience has dented my confidence only slightly in a car that has otherwise shown no sign of weakness at all. It even came out well when we drove it back-to-back with an M5 Touring, with most people saying the 535d was every bit as desirable as the sportier car.

Everyone who's driven our long-termer has been impressed by its space, quality and road manners - and blown away by the engine. So far, I'm the only one to have bought it flowers, though...