2021 BMW 540i xDrive First Test: Quick, But Not Exactly Fun

The seventh generation of the BMW 5 Series, coded “G30,” has not earned universal praise at MotorTrend as had some earlier models. When it competed in our 2018 Car of the Year contest, we chided its “numb handling and response” and lamented “an anodyne feel that permeates all of these 5 Series entries.” We attributed that […]

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The seventh generation of the BMW 5 Series, coded “G30,” has not earned universal praise at MotorTrend as had some earlier models. When it competed in our 2018 Car of the Year contest, we chided its “numb handling and response” and lamented “an anodyne feel that permeates all of these 5 Series entries.” We attributed that largely to BMW’s decision to migrate the 5 to the architecture that underpins the larger, heavier 7 Series. In our luxury midsize category rankings, the 5 has trailed the Mercedes-Benz E-Class, Audi A6, and at times even the Lexus ES.

Well, BMW has sharpened its pencils and rolled out a revamped G30 5 Series for 2021. This new 5 Series boasts loads of detail improvements, including a 48-volt mild hybrid system for the heart-of-market 540i, in direct competition with the similar mild hybrid setup found in the Mercedes E450. Is it enough to bump the 5er up in our rankings? With its new mild hybrid system, is it the best luxury hybrid sedan?

How Quick Is the 2021 BMW 540i xDrive Mild Hybrid?

The short answer may be “as quick as it needs to be to dice with its archrival from Sindelfingen.” Yes, inline-six engines augmented with 48-volt mild hybridization are this season’s “new black” in engine-compartment couture. We recently tested a Mercedes-Benz E450 4Matic sedan powered by just such a powertrain rated at 362 hp and 369 lb-ft, and it zipped to 60 mph in 4.6 seconds en route to a 13.3-second, 103.2-mph quarter mile. It also helped that model win our 2021 Car of the Year award.

Our 540i xDrive managed to hit those respective marks in 4.6 and 13.2 seconds with a 106.1-mph trap speed. At first that seems impressive given that the BMW makes do with eight transmission ratios while the Benz gets nine, but then you do some math and realize the Mercedes’ overall gearing is notably taller, likely in an attempt to claw back some fuel economy for its heavier cars. Our test BMW weighed 171 pounds less and is EPA-rated 2 mpg higher on the highway and 1 mpg higher combined (23/32/27 mpg versus the Mercedes E450 4Matic’s 23/30/26).

The last 540i we tested, a 79-pounds-lighter, rear-wheel-drive 2017-model-year example sans electrification, needed 4.9 seconds to hit 60 mph and did the quarter in 13.5 seconds at 106.2 mph. BMW claims that difference is entirely down to the xDrive’s improved traction—indeed, BMW’s current zero-to-60-mph estimates match our results perfectly (4.9 seconds for the hybridized rear-driver, 4.6 for the xDrive).

So What Does the Hybrid Drive Contribute?

Well, if not speed, there is an EPA combined fuel economy bump of 3 mpg with rear drive and 4 mpg with xDrive attributable to the mild hybrid bits. Beyond that, BMW refuses to divulge torque specs for the 540i’s belt-alternator-starter unit, stating only that it contributes 10.7 horsepower. Not divulging a torque number allows BMW to avoid explaining a difference between motor torque and its contribution to crankshaft torque.

See, Mercedes sandwiches the E-Class’ EQ Boost motor between the engine and transmission, where it contributes its 21 hp and 184 lb-ft directly to the crankshaft. By contrast BMW’s alternator-starter delivers torque via a belt and pulleys, so the crankshaft contribution gets multiplied by the difference in those pulley diameters (which I measured as 2.25 inches on the alternator and 6.75 inches on the crankshaft). So if the motor generates 45 lb-ft (a typical value for such devices), that would amplify to 135 lb-ft at the crank. What these mild hybrid motors mainly do for their turbocharged engines is erase any sensation of initial boost lag because they make their biggest power/torque contribution at the moment you hit the accelerator. Electric assist then tapers off as turbo boost builds. The driver never feels anything but smooth, linear acceleration in either of these cars.

Hybrid = Sportier Sport Mode

Having an extra electric motor and 0.48-kWh battery on board gives the computer programmers one more dial to twist when programming the drive modes. Sure enough, when you engage Sport or Sport+ mode in the 540i, the system aggressively tops up the battery to ensure that no matter how close together the corners are on your favorite back road, you’ll have full battery assist power on tap at every corner exit. Drop back into EcoPro or Comfort mode, and the system allows the battery state of charge to resume hovering at around 60 percent to leave room for recovering energy when coasting or braking to a stop.

So Is the BMW 540i the Best Luxury Hybrid Sedan?

Heavens, no. It’s not even the best luxury hybrid 5 Series. That honor goes to the plug-in 530e, which augments a slightly depowered 2.0-liter turbo-four with a bigger 107-hp, 77-lb-ft motor mounted in the transmission and powered by a 12.0-kWh (9.1 kWh net) battery. With a combined output of 288 hp and 310 lb-ft, the 530e shaves a couple precious tenths off the gas-only 530i’s acceleration times for a 6.0-second dash to 60 mph and a 14.4-second, 97.5-mph quarter-mile run while delivering 65 or 69 mpg-e (AWD vs. RWD) combined fuel economy in mixed gas/electric driving.

Adding a battery and a fancier alternator has done little to address our concerns about the anodyne nature of the ostensibly sportier 540i’s driving experience. After all, it’s still based on bigger, heavier 7 Series underpinnings. We older staffers still vividly remember the glory years (mostly the 1990s E34 and E39 generations) of 5 Series dynamic brilliance, and we still miss it. That doesn’t mean the new 540i is no fun to fling around a technical stretch of abandoned roadway. On the contrary, its dynamic behavior is largely faultless, the car never puts a wheel wrong, and we never found ourselves needing to modify a steering or brake input midcorner. Its transmission instinctively selects the best gear for every situation in the Sport modes, its shift paddles bring instant shifts when desired in Comfort mode, and the ride control remains firm yet supple. We just wish for more road feel at the steering wheel rim and to be less aware of variation in the ratio as speed changes, and to feel more moved by the whole experience.

And Is the Midcycle Refreshed 5 Series a Better Luxury Car?

Yes, the relentless march of progress improves all cars, and the refreshed 5 Series is no different; the interior of this 540i is swathed in rich-looking mocha leather with abundant contrast stitching and piping and interesting ventilation perforation patterns. But the general design of the interior continues to trail the interior designs of the Audi A6 and Mercedes E-Class. We applaud BMW’s extensive efforts at presenting interesting infographics on the many configurable cluster, center, and head-up displays, and the iDrive control knob is by now a known quantity and an acknowledged leader in the infotainment user experience, ranking well ahead of the most recent redesign of the Mercedes-Benz User Experience (MBUX). But in the aggregate and considering all the key criteria on which we judge Of The Year contenders, the BMW 5 Series still trails the Audi A6 and Mercedes E-Class while outperforming the Lexus ES, Genesis G80, and Volvo S90 in our segment rankings.

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