After eight years of ownership, it was finally time to say goodbye to my BMW Z4. What started as a simple plan to trade it in quickly turned into something unexpected — a last-minute private sale that brought in more money than the trade-in offer. That twist of fate made the next chapter even sweeter: collecting my new BMW M135i.

This isn’t just another hot hatch purchase. It’s a major step forward in performance, comfort, and technology — and after my first 48 hours with the car, I have plenty to say.

Why Upgrade from a BMW Z4?

For context, my previous car was a BMW Z4 sDrive20i producing 184 horsepower with a 0–60 mph time of 6.6 seconds. It was quick enough to be fun, and over eight years I grew completely accustomed to its low stance, firm suspension, and two-seat layout.

But technology moves fast — and so does performance.

After nearly a decade with the Z4, I wanted:

• More power

• Modern technology

• Everyday practicality

• Increased comfort

• A fresh driving experience

The M135i ticked every box.

2021 BMW M135i Performance: 306HP of Everyday Madness

The 2021 BMW M135i delivers:

• 306 horsepower

• 0–62 mph in 4.8 seconds

• 2.0-litre turbocharged four-cylinder engine

• xDrive all-wheel drive system

Coming from 184 horsepower, the jump is dramatic. The acceleration is instant. In fact, it’s almost too easy to reach motorway speeds. What used to feel like a build-up of momentum in the Z4 now happens in seconds.

There’s a genuine learning curve when stepping into a car this quick — especially when you’ve driven manuals for over 20 years and suddenly switch to your first automatic. Yes, this is my first automatic car, and it’s taking some adjustment. I still instinctively look for the clutch.

But once you settle in, the smoothness of the gearbox combined with the punch of the turbocharged engine makes daily driving effortless.

Comfort vs. Sports Car Stiffness

One of the biggest surprises has been comfort.

The Z4, sitting on low-profile 19-inch wheels, transmitted every bump in the road. Over time, that becomes normal. You brace yourself for potholes. You expect rattles. You feel every imperfection.

The M135i? It glides.

The suspension setup is far more forgiving without sacrificing handling capability. Road imperfections that would have jolted the Z4 barely register here. The sports seats are incredibly supportive — bucket-style, body-hugging, and perfect for long drives.

I completed an 18-mile journey home in heavy rain on day one, and even in poor conditions the car felt planted and composed.

Interior Technology: A Huge Step Forward

If performance is the headline, technology is the real upgrade.

The 2021 M135i feels generations ahead of the older Z4. This particular car was clearly spec’d generously from factory. It includes:

• Heads-Up Display

• Heated steering wheel

• Electric memory seats

• Parking assist

• Rear-view camera

• Comfort Access

• Electric tailgate

• Ambient interior lighting

• Panoramic sunroof

• Tracking system

The ambient lighting deserves a special mention. Unlike some competitors where lighting can feel overwhelming, this setup is subtle and tasteful — enhancing the cabin rather than distracting from it.

The Heads-Up Display is another feature I didn’t know I needed until I had it. Speed and navigation information projected directly onto the windscreen changes the driving experience entirely.

Running Costs: Fuel Comparison

A full tank costs around £60, which is surprisingly similar to what I paid with the Z4. Given the power increase, that’s reassuring.

Insurance may benefit slightly thanks to the factory tracking system — something I’ll be confirming with my provider.

Is the M135i Better Than the M140i?

The natural comparison is the BMW M140i, often praised for its inline-six engine and rear-wheel drive setup.

While the M140i has undeniable appeal, I wasn’t quite ready to step into a six-cylinder yet. The four-cylinder M135i offers more than enough performance for daily driving while delivering superior interior technology and refinement in this generation.

For me, this was about balance — performance combined with modern comfort.

First 48-Hour Verdict

After two days and roughly 200 planned miles ahead, here are my early thoughts:

Performance: Extremely quick, bordering on outrageous for daily roads
Comfort: A major improvement over my previous car
Technology: Game-changing compared to an older sports coupe
Practicality: Five doors, usable boot, real everyday versatility

It feels like a serious upgrade in every measurable way.

Will I miss the Z4? Perhaps in peak summer with the roof down. But with the panoramic sunroof open and 306 horsepower under my right foot, I don’t think I’ll be dwelling on the past too much.

What’s Next?

This is just the beginning. There’s still a lot to explore:

• Long-term ownership costs

• Real-world fuel economy

• Winter driving performance

• Maintenance expectations

• Detailed feature breakdown

If you’re considering a 2021 BMW M135i as a daily performance hatchback, early impressions suggest it delivers a strong blend of speed, comfort, and modern tech — all in one package.

The era of the Z4 has ended. The M135i chapter has officially begun.