Understanding the 4 Series: Where Sport Sedan Meets Coupe
The BMW 4 Series isn't a separate platform—it's the coupe and convertible variant of the 3 Series, plus the four-door Gran Coupe (introduced 2014). This matters because the 4 Series inherits both the strengths and weaknesses of its parent generation, but in a sportier chassis designed for handling over practicality.
If you're shopping 4 Series, you're making an aesthetic choice as much as a mechanical one. The reliability profile follows the 3 Series exactly, but the driving experience emphasizes performance and dynamics. That changes what matters when you're buying.
F32/F33/F36 (2014–2020): The First Generation
The F32 coupe, F33 convertible, and F36 Gran Coupe came with three engines, and your choice here is critical: the N20 (428i), the N55 (435i), and the B58 (440i).
The N20 428i: Timing Chain Risk
The N20 is the 428i's engine, and it carries the same timing chain vulnerability as the F30 3 Series 328i. Expect potential chain stretch between 60K and 100K miles. If you're considering a used 428i, factor in the timing chain risk and budget accordingly, or seek N55/B58 models instead. A 428i at a discount price usually means the timing chain is on someone's mind.
The N55 435i: The Sweet Spot (With a Caveat)
The N55 responds beautifully to tuning, making it popular with enthusiasts. If you find a well-maintained example, it's a solid buy. Just listen for that rattle on the test drive.
The B58 440i: Excellent
The B58 is BMW's modern twin-turbo inline-six, debuted in 2015 as the 440i engine. It's significantly more durable than the N54 or N55, with stronger internals, better turbo design, and proven reliability. The 340 hp output is real, and the engine scales well with tuning. If you can find a B58 4 Series, it's the least stressful choice mechanically.
G22 (2021+): The New Generation
The G22 coupe and G82 M440i represent BMW's latest thinking. The standard B48 engine is refined and reliable. The M440i uses the B58 with 48V mild-hybrid assistance, adding about 50 hp and improving throttle response. This is a genuinely modern platform with iDrive 7, updated cabin tech, and no known generation-wide issues yet.
If budget allows, the G22 M440i is a compelling choice: the B58 is proven, mild hybrid tech is transparent (you won't notice it), and the driving dynamics are sharp. Maintenance follows standard modern BMW practice: brake fluid every two years, cabin filter, standard wear items.
Buying Advice by Engine
Budget Buyer: N55 435i (F32/F33/F36)
Performance Enthusiast: B58 440i (F32+)
The B58 is the engine to own if you plan to modify or drive spiritedly. It responds to tuning without question, has stronger internals than the N55, and the cooling system is more robust. Whether F32 440i (post-2015) or G22 M440i, you're buying an engine that'll handle your plans without regret.
Avoid: N20 428i
Unless heavily discounted and you've budgeted for timing chain work, skip the 428i. The power is modest (240 hp), and the timing chain risk negates any fuel economy advantage. The N55 335i offers better performance for similar money, and the B58 440i offers modernity without the headache.
What the 4 Series Buyer Should Know
The 4 Series is a sport car, and sport cars require more discipline than daily sedans. Brake wear is higher (performance-oriented chassis + turbo power = spirited driving). Tire life is reduced by aggressive geometry. The convertible top (F33) requires periodic cleaning and lubrication, or it'll fail faster.
If you're buying used F32/F33/F36, factor in cumulative mileage costs: brake fluid every two years, quality brake pads every 40K–60K miles (more if you drive the twisty road), and plan for eventual strut replacements. The fun is real, but so is the cost of keeping it sharp.
The Verdict
The 4 Series is the coupe for buyers who want genuine performance without the M3 price tag. Pick the N55 for value, the B58 for reliability and modernity. Avoid the N20 unless you're getting it for steal prices and you've educated yourself on timing chain risk. The G22 is the sensible new-car choice if budget allows.