2012 BMW 528i Long-Term Update 3
Efficient Dynamics - Part Two
Now that our long term BMW 528i has wound over 17,000 miles onto its odometer and we have all of our track test numbers in hand, we're finally in a position to address what I've called this car's Big Trade-off: Is it really both Efficient and Dynamic, per BMW's new green-age slogan? And more pointedly, is it dynamic enough to simultaneously be an Ultimate Driving Machine?
Recently I'd begun to address the car's mileage when its overall mileage (since arrival) had settled-down at 24.8 mpg. And when I say 'settled down' I really mean it. Despite its seeing a bunch of mileage-helping long-distance highway drives since then, these have only fractionally elevated overall number, now at 25.1 mpg. In other words, the 528i, in our hands, is basically a 25 mpg car (the EPA's combined number is 27). Here's a graph I showed you last time (updated with our latest figures), but I'm presenting it again because I think it's a nice reminder of why we've needed to wait awhile before claiming what the car's mileage is: What you're looking at is a running average since we began logging the 528i's fill-ups. And notice again that it's taken until about the 7000 miles before we have a number we can confidently point to.
So here's the question: is a car that returns 25.1 mpg, and scoots to 60 mph in 6.2 seconds, a car that's simultaneously 'Efficient' and 'Dynamic'? To get a handle on this, we need to put it into perspective. Via Motor Trend's database, I've sorted-out a group of sedans (44, as it happens) from our last three years of testing, all of them having premium, or near-premium, nameplates. Notably, almost all of them also have more power than the 528i's meager 240 hp - which is only slightly offset by its being it's modestly lighter than the group's average. So to put all these cars on a comparable footing, we'll be looking at their hp-per-lb ratio instead. And so in the next two graphs I've plotted the cars' EPA combined mpg's (along the bottom, X-axis) against their lbs-per-hp and lateral grip (that's derived from the Figure-Eight handling course). In addition, I've color-coded the various flavors of power production represented (traditional gasoline, turbocharged gas, supercharged gas, hybrid, diesel and turbo diesel).
Here we've plotted each of our 44 car's lb/hp against their EPA combined mpgs. If a dot is farther to the right, then its mileage its better; and if a dot is higher, it's likely to have better performance. In other words, an efficient and dynamic sedan wants to be is as close to the upper right corner as possible. What do we make of the BMW 528i? Not much. It's seems to be along the curve of the better cars, though on the low-ish performance edge of it. Notice that the Infiniti M35h and Lexus GS 450h (hybrids, both) are two clearly better positioned cars.
This graph of lateral grip versus combined mpg should be read in the same way as previous one: the closer to the upper right corner a car is, the better its combination of cornering grip and mileage. Here, the 528i looks a little better, clearly offering a nice combination of both qualities. Of course you might wonder what the connection is between the cornering performance and higher efficiency. Well, it depends on what sort of efficiency-enhancing technology we're talking about. A hybrid is likely to be heavier (bad) while here, a four-cylinder with a turbo (swapped in place of a six), saves weight, and specifically on the car's front wheels (meaning better handling balance as well). To wit, our long term 528i is roughly 110 lbs lighter than a BMW 535i we recently tested. But again, it's hard to ignore those pesky two hybrids, the GS 450h and M35h, which look to be higher mileage alternatives offering similar grip. Moreover, at real-world speeds, the 528i frequently exhibits lots of spontaneous lateral wiggles on moderately irregular roads, as well as very lazy response when you stamp on throttle (gee, that sounds like a good topic for a future update!).
So there we are. Does the BMW 528i truly represent Efficient Dynamics? Yes -- how about we spell that in all lower case.
|Service life||9 mo/17,565 mi|
|Average fuel economy||25.1 mpg|
|CO2 emissions||0.77 lb/mi|
|Energy consumption||134 kW-hr/100 mi|