The 2021 Audi S4 is a sporty compact luxury sedan that blends everyday comfort with serious performance, positioned as the high-output version of the A4 and a direct rival to cars like the BMW M340i and Mercedes-AMG C 43. It’s ideal for drivers who want a refined commuter that can also handle spirited back-road driving without moving up to a larger, less agile sedan. For 2021, the S4 continues the B9-generation (B9.5 refresh) updates introduced for 2020, including updated styling, tech, and interior refinements. The result is a well-rounded sports sedan with strong acceleration, all-weather quattro traction, and premium cabin quality.

1) Turbocharged V6 performance: The 2021 Audi S4 uses a 3.0-liter turbocharged V6 (single turbo) producing around 349 horsepower and 369 lb-ft of torque, delivering quick, effortless passing power. 2) 8-speed automatic with quattro AWD: An 8-speed Tiptronic automatic is paired with Audi’s quattro all-wheel drive for confident traction in rain or snow and stable power delivery under hard acceleration. 3) Sport-tuned chassis: Standard sport suspension and performance brakes give the S4 sharper handling than the A4, with available adaptive damping (depending on packages) to balance comfort and control. 4) Modern infotainment and cockpit tech: A 10.1-inch MMI touch display is standard, and many models include Audi’s Virtual Cockpit digital gauge cluster for a customizable, high-end driver display. 5) Premium interior with practical space: Supportive sport seats, upscale materials, and a usable rear seat and trunk make it a true daily-driver performance sedan rather than a weekend-only toy.

Shoppers often search “2021 Audi S4 problems,” “2021 Audi S4 reliability,” and “2021 Audi S4 common issues” because this model combines high performance with complex electronics and turbocharged hardware. Overall reliability is competitive for a modern German sport sedan, but there are a few patterns owners and technicians frequently mention. 1) Thermostat/water pump and coolant leaks: Some 3.0T Audi engines are known for cooling-system component seepage over time. On the 2021 S4, owners may report coolant smell, low coolant warnings, or slow leaks that can show up anywhere from roughly 20,000 to 60,000 miles, depending on driving conditions and heat cycles. 2) Infotainment and electronics glitches: MMI touch display lag, Bluetooth/CarPlay connection dropouts, or intermittent sensor warnings (parking sensors, driver assistance alerts) are common modern-car complaints. These issues are often software-related and may be resolved by updates, resets, or module replacement in more persistent cases. 3) Suspension noises and bushing wear: Clunks or creaks over bumps can occur as suspension bushings and mounts wear, especially on cars driven on rough roads or with aggressive tires. Some owners notice this in the 30,000–70,000 mile range, though it varies widely by road quality and driving style. 4) Carbon buildup on intake valves (long-term): The 3.0T is direct-injected, which can contribute to intake valve deposits over time. It’s more of a higher-mileage concern (often 60,000+ miles) and may show up as rough idle, reduced efficiency, or performance that feels less crisp.