There have been times in the past at the launch of an all-new BMW 5-series when we have questioned the merit of tests such as this. We've always gone ahead with them because you cannot prejudge such encounters, but since at least the launch of the E34 5-series back in 1987, the result has always gone the same way. Five meets Mercedes E-class, Five beats Mercedes E-class, Five goes home. That's 23 years of fairly foregone conclusions.
BMW has run out of E numbers now, so this generation is called F10, but it wasn't so much anything about the 5-series that made us relish this particular contest more than any similar encounter in the past two decades; it was something about the E-class. Before either squared up in the Portuguese sunshine, we didn't merely suspect that this would be the toughest fight of the Five's life; we near enough knew it.
Never has the E-class stood so proud of its class as this one does today. It has already pasted the outgoing 5-series, a car for which we have no shortage of affection, and dusted the Jaguar XF. Moreover, it's never better than when fitted with Mercedes' 3.0-liter diesel motor, precisely the weapon we have lined up to take on the 530d, historically the best of the basic 5-series.
No longer will it be good enough for the Five merely to be more fun than the E-class, because the Mercedes has come on so far in so many other areas; the BMW must compete on all fronts. It will need ride and refinement unapproached by any predecessor, a proper rear seat package and huge improvements in quality, both perceived and real.
If it also retains all of its hitherto unrivaled capacity for driving pleasure, then it might lay credible claim to its once-assumed class dominance. Otherwise this story may have a rather different ending from all previous confrontations.
Both cars look disappointing. The Mercedes is odd, the BMW just bland and unimaginative, as if the company started to retreat from the oft-criticized Chris Bangle school of edgy design and didn't know when to stop. In the metal it has little presence, though that's probably preferable to the Merc, whose considerable presence serves only to remind you how unattractive it is, especially around the nose.
Inside the 530d, BMW has made useful progress, and whether its cabin is preferable to its rival's depends on your priorities. Certainly it works better; its switchgear is more lucidly arranged, its dials are clearer, the new iDrive controller clearly superior to Mercedes' rival Comand system. There's a clean, airy feel to the driving environment, backed by a flawless driving position and excellent visibility.
What it lacks is a sense of occasion. For all its efficacy, this is not the cabin of a luxury car, whereas that of the Mercedes undoubtedly is. Less coherent is may be, but the way the E-class deploys its wood and leather and subtle but extensive use of chrome has a class missing from the BMW.
The Mercedes is also going to make better friends with those who elect to travel in the back, but no longer by much. The real news is how close the BMW now comes to offering E-class interior space. In neither car will any less than the freakishly tall be troubled for head room, and for once the E-class's advantage on leg room has been much reduced. Indeed, for the first time in its 28-year history, the Five can claim at last to seat four large adults in comfort. Its trunk is fractionally smaller.
But what you really want to know is, which car is better to drive. And the perhaps surprising answer is that this is an extremely close-run contest, determined by nuances here and there and a presumed order of priority that some customers may not share. BMW, whose supremacy in this area is measurable in decades, would be correct to be concerned by this.
Most importantly, both are fine cars to drive fast or slow, in a straight line or through some corners. The paper advantage belongs entirely to the BMW, which offers a little more power and markedly better acceleration, whether you choose the standard six-speed manual (and make your car difficult to sell), or join the other 95 percent who will choose the optional eight-speed auto fitted to the test car.
This new gearbox works brilliantly, better than the six-speed auto it replaces and the seven-speed unit used by Mercedes. Somehow, it seems always to be in the right gear without perpetually hunting around for the optimum ratio. It knows exactly when to change down and when to keep its nose out of the engine's business and let the torque do the work.The E-class answers the way a Mercedes should. It can't match the BMW engine objectively, because its 0-62mph time of 6.9sec is 0.6sec off the 530d's benchmark. Instead, it contents itself with being quieter, smoother and, as a result, more sophisticated, while still being plenty swift enough to offer all the performance most buyers will ever want (or indeed use).
There is greater distinction between the two in the way each tackles a challenging stretch of road, but at the end even more head scratching is required to determine whose approach is better.
The BMW is easier to drive, the kind of car any reasonably skilled and experienced driver would be confident driving hard upon first acquaintance. Its wheelbase has been extended by 80mm, explaining not only all that extra interior space, but also its uncanny stability at speed. Even if you turn off all the electronic safety nets (the Mercedes allows only partial disablement), it remains stoically planted and easy to keep on line. The 5-series requires provocation of a kind a statistically negligible number of owners will dole out to unsettle it.
It's not like this in the Mercedes. At first it feels like a bigger car – though the BMW is both longer and wider – and you find yourself taking more care with your lines. It's more softly sprung and rolls more as a result, and despite similar test car tire specifications, it offers a little less grip. But it still has a trick or two up its sleeve; it just takes a little more time to show them to you.
First, it has better steering. BMW has moved to an all-electric system for the Five, and while that's doubtless good at lowering emissions and improving fuel economy, it comes with a slightly artificial feel that not even BMW can disguise. The Mercedes' steering feels smooth and almost liquid by comparison, free of friction and wonderfully linear and precise.
Secondly, and still more surprisingly, it's actually slightly better balanced than the BMW. The 5-series understeers a little, the Benz barely at all. It doesn't attack corners like the Five, but instead flows beautifully through them, proving once and for all that soft need not mean flabby any more than hard automatically equates to harsh.
But move onto traditional Mercedes territory and while the distinctions are there, once all have been taken into consideration, the two remain damnably difficult to separate. There is no question, for instance, that the E350 CDI offers significantly better ride quality than the 530d. But this is only because the Mercedes is perhaps the finest-riding car ever to wear steel springs.
No one choosing standard suspension is going to return their 5-series complaining that the ride is too stiff, for this is the most comfortable Five in history, and by some margin. Besides, over long distances we can see some owners even preferring the more taut feel of the 530d and appreciating its notably better fuel consumption (45.6mpg with auto 'box vs 40.9mpg).
Even so, it is the Mercedes that is the quieter of the two. At a steady cruise its advantage extends only to slightly lower levels of wind noise, but when you're stop-starting in town or pressing on down a country road you hear a lot less of the engine, a phenomenon that helps bolster the sense of opulence and luxury that so distinguishes the E-class. Perhaps BMW has planned it that way, believing that its historically more sporting customers may prefer to hear a little more of its straight-six snarl than Mercedes' V6 growl.
And so the pendulum continues to swing, conferring no outright advantage on either side. Eventually however, clarity arrives. Perhaps what matters more even that the identity of our victor, though, is that for the first time in too long, the BMW 5-series and Mercedes E-class no longer represent variations on a similar theme, but two entirely distinct and individual approaches.
The BMW remains a BMW, albeit one where ease of ownership has become as important as driving dynamics. It's a more complete car than the old model, and if that means it's lost a little of the old enthusiasm, some would argue that this is a price worth paying for its broader base of talents.
But the Mercedes does not remain a Mercedes; it has become one again. It bears repeating that the E-class's greatest strength is that it has stopped trying to chase the 5-series and has rediscovered the values of quality, comfort and luxury upon which not just the brand but its marque should stand.
When all is added up, there may not be much between these two, yet they are gloriously different cars. And the truth is that the final determinant of which is best for any given customer won't be one car's clear superiority over the other, but which talent set is most appropriate to the buyer's desires and circumstances.
Still, we've come too far and driven for too long not to answer the question, and I'm going to give the nod to the Mercedes.
I'm not going to weigh up all the pros and cons of either competitor again, but instead leave you with the following thought. If these cars are all but inseparable on the road, what's left are the feelings they leave you with when parked outside your house. For while I might agonize over which one I'd prefer to drive on any given day, I'd find
it less of a struggle to decide which one to live with month by month. And it would be the Mercedes.