I Drove Two Of The Fastest Plug-In Hybrids. My Favorite Will Surprise You

Carmakers are now stuffing big batteries into their loudest and proudest performance flagships—the cars in their lineup that typically have the highest emissions—and it has created a crop of cars that are quite odd. They are absurdly quick in a straight line and can take you dozens of miles on electricity, but the heavy hybrids start to fall apart when you try to throw them into a corner like their non-electrified predecessors.

This became apparent after driving the new G99 BMW M5 Touring and then jumping into a Mercedes-AMG C63s E-Performance. One has a big V-8 complemented by a big battery that gives it dozens of miles of electric range, while the other has a small four-cylinder, with a smaller battery whose purpose is mainly to increase performance. Two very different approaches that at launch drew a lot of critcism from fans and keen drivers, but for different reasons.

Photo by: Andrei Nedelea

Photo by: Andrei Nedelea

The new BMW M5 feels even more gutsy than its claimed 717 horsepower output would suggest. It’s not surprising that one dyno test revealed that it was pushing almost 700 hp to the wheels, meaning the real output is probably closer to 800 hp. It pins you to your seat with its alarming pace, whether from a standing or a rolling start. There’s nothing quite like feeling the shove of a 4.4-liter twin-turbocharged V-8 engine with 737 pound-feet (1,000 Nm) of torque.

The M5’s powertrain is unequivocally brilliant. Part of that comes down to the fact that it’s also pretty great to drive without firing up the V-8. With 197 hp and 206 lb-ft (280 Nm) of torque, the electric motor, which lives inside the eight-speed automatic gearbox, is more than capable of moving the M5 on its own. Even in my hefty, 5,456-pound (2,475 kg) Touring Model, the M5 felt brisk in EV mode. 

The M5 provides around 35 miles of pure electric driving.

Photo by: Andrei Nedelea

I found myself enjoying driving the M5 most in EV mode, surprisingly. It pipes in a subtle, fun acceleration sound through the speakers. It also shifts up through the gears when the V-8 is off and you feel the shifts, although you can’t control them yourself in EV mode. The electric motor sends its power to all four wheels, meaning that even driving in EV mode in winter or low-grip conditions, you know you can rely on the all-wheel drive system’s reassuring extra traction. It’s a great around-town electric experience no matter the weather.

After driving the M5 Touring and putting a few hundred miles on it, I kind of wished I was driving the pure electric i5 Touring M60 instead, a thought I never expected. The new M5 is the first BMW M that I didn’t instantly covet after driving. Because it’s so heavy (heavier than the i5), BMW has had to tune the suspension to cope with the mass, and it results in a weirdly inconsistent ride quality. It can’t decide if it’s a Maybach or a pogo stick and you never know which of those extremes you’ll get.

Mid-corner bumps also unsettle the car, often alarmingly, and you feel the transfer of forces from one side to the other as you thread the car around a twisty road. All this mass makes the M5 feel like an athlete trying to run with ankle weights on. There’s an uncomfortable amount of inertia trying to pull the car straight into understeer when you drive it spiritedly.

Then I jumped into the still heavy but far more agile Mercedes-AMG C63 PHEV, and it really put the M5’s mass into perspective..

I know it’s one size class below the M5, so it’s not a direct and totally fair comparison, but I would honestly pick the C63. Yes, it only has four cylinders, which is half of what the BMW has, and a few dozen fewer horsepower. But it feels more special to drive. And while its engine may only be a 2.0-liter, it’s an actual AMG engine hand-assembled by someone who puts their name and signature on it.

Photo by: Andrei Nedelea

The signed plaque is proudly displayed when you pop the hood, and you also get to see the big turbo and electric supercharger setup sitting to the side of the engine. This was a more impressive sight than what I saw when lifting the hood on the M5, whose clever hot-V twin-turbo setup is hidden by an underwhelming plastic engine cover.

The M139 engine is borrowed from the hottest versions of Mercedes-AMG’s compact offerings, like the CLA 45. It makes well over 400 horsepower on its own, and together with the electric motor, puts out 670 hp and 752 lb-ft (1,020 Nm) in the C63. That’s more torque than the BMW in a car that’s about 880 pounds (400 kg) lighter, and you can really feel it.

Photo by: Andrei Nedelea

The force that acts on your body when you do a Race Start in the C63 is unlike anything I’ve ever felt in a combustion car. It definitely feels faster than the BMW, even though on paper, they are fairly evenly matched. Just like the BMW, the Mercedes feels quicker than the numbers suggest, but by an even greater margin. It’s shockingly quick off the line, thanks to all that torque and its all-wheel drive that does a fantastic job of putting the power to the ground.

There’s also an electric supercharger working to build boost quickly and minimize lag. The powertrain is really responsive, and the surge you feel from the combined torque of the electric motor and gas mill is really something. It doesn’t sound as bad as some have said, even if you disable the piped-in enhanced engine sound. You still hear the exhaust, which is characterful, and you get to hear the turbo build pressure and release it, which, for me, added to the fun.

It’s also much more enjoyable through the corners than the M5. It doesn’t feel like the C63s of old, which were always all too eager to turn their rear tires into shreds and smoke. The new model feels like a track car, focused on delivering the best possible corner exit with minimal drama.

Photo by: Andrei Nedelea

Sure, the C-Class on which the C63 is based is smaller and lighter than the G61 5 Series Touring that serves as the basis for the M5. However, there isn’t an E63 that we can compare it to (yet), and the E53 plug-in hybrid that I have driven is not in the same performance league as the M5 and C63, even though its widebody treatment suggests it would be.

Mercedes could have ended up with a PHEV that was nearly as heavy as the Bimmer, but it intentionally designed a lighter system. Unlike the M5 and E53, which have a similar battery and motor configuration as lesser PHEV versions of each model, the C63 gets a smaller, bespoke setup. Its electric motor isn’t located in the gearbox but integrated into the rear axle, and its main purpose isn’t to drive the car around in EV mode (even though it can do that for around 5 miles). It’s there simply to boost performance, which it does in spades.

Photo by: Andrei Nedelea

Mercedes’ real genius move with the C63 was giving it a smaller battery. While the M5 has a 22.1-kilowatt-hour battery, which is largely to blame for its heft, the C63’s battery only has a capacity of 6.1 kWh. That’s small by PHEV standards, but it does the job, and that job is mostly regulatory—it needs to do well in lab testing to please the European Union’s increasingly stringent emissions standards.

The heavier, more powerful of the two, the BMW, gets a WLTP efficiency rating of between 1.6 and 1.7 liters/100 km, or almost 150 mpg. However, that’s only if you keep the battery topped up, which many PHEV drivers don’t, which is why the M5’s EPA combined rating of 13 mpg (18 l/100 km) is much closer to what it actually returns in normal driving.

The C63 doesn’t get a comparable efficiency rating in Europe, with a claimed average of 6.9 l/100 km or 34 mpg. You will have to be extremely gentle with the throttle to come anywhere near that, but it is achievable, even with a drained battery. Driving it like I did the BMW to enjoy the car rather than save fuel, it ended up returning around 15 mpg, which is still excellent given the ludicrous acceleration that it can provide. The EPA rates the C63 at 20 mpg with a depleted battery, which is definitely achievable without trying to drive especially efficiently.

Look, we’re InsideEVs—we love electrons. But in performance cars, more battery isn’t always the way to go. The people who buy these cars can afford to fuel them up, and the advertised and often unrealistic efficiency numbers are not a key selling point for someone looking for a C63 or an M5. Plus, performance cars are a tiny subset of overall vehicle sales, accounting for a tiny fraction of overall emissions. We can electrify mass-market cars today, which would pay far greater dividends. But as the M5 proves, if you want the best possible driving experience, a giant battery can get in the way.

Even though Mercedes is accused of doing it wrong, I think it has the right approach to making a performance PHEV. The C63 is a better driver’s car than the M5, which is just too heavy to be fun. The C63 is still heavier than it would have been had Mercedes stuck to a V-8 without electrification, but for a PHEV, it’s still an excellent and exciting driving experience. It feels more special than the M5, even with half the cylinders.

There should be a clear distinction between electrified cars designed for efficiency and those where electrification is meant to enhance performance. Some great performance PHEVs include the second-generation Acura NSX, the Corvette E-Ray, the Ferrari 296 GTB or the new Lamborghini Temerario. Sure, electrification does enhance efficiency to a degree in any application, but making a PHEV too heavy by giving it too big a battery can make it less efficient than the same car powered solely by combustion.

Gallery: 2025 BMW M5 Touring

What Mercedes-AMG did with the C63 PHEV is closer to Ferrari’s plug-in hybrids, where efficiency is never the key point of focus. The battery doesn’t have to be huge, and in cars like the Ferrari SF90 and 296 GTB, it’s under 8 kWh, which doesn’t overburden the chassis and keeps these cars’ handling pure. Getting a few miles of electric driving is a bonus, but the main point of the electrification remains performance.

The only catch is that if the battery runs low, the engine turns into a hamster wheel, sapping power to make electricity to replenish the pack. Unless you’re doing several laps of the Nurburgring, that likely won’t matter. I drove the C63 quite hard around a twisty road for over half an hour, and it still showed around 33% battery remaining. Maybe if you take it on a track where you keep the throttle pinned for longer, you will feel the performance loss, but in my experience, there was none.

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