Used Audi S4 B9 (2018-2024): Buyer's Guide

The B9 Audi S4 dropped the supercharged V6 and the manual gearbox that defined the previous generation. In their place: a single-turbo 3.0-liter making 349 horsepower and a ZF 8-speed automatic that owners on AudiWorld and Audizine largely trust more than the dual-clutch box it replaced. That trade bought smoothness. It didn't buy a clean bill of health.

Early production cars, mostly 2018 and some 2019 models, carry a well-documented rocker arm failure that turns into an engine-out repair well north of $5,000 if it's ignored. Audi quietly revised the part partway through the run and never issued a recall for it. If you're cross-shopping model years, that single fact should shape which car you buy more than trim level or color.

This guide covers the full B9 run: 2018 launch through the 2024 model year, after which Audi folded the S4 sedan into the S5 nameplate for 2025. One engine, one transmission, three trims, and a handful of failure points worth knowing before you sign anything.

The B9 competed against the BMW 340i/M340i and Mercedes-AMG C43 through most of its run, and it split the difference between them: quicker and grippier than the BMW in bad weather thanks to standard quattro, less overtly sporty than either rival because Audi tuned the B9 toward comfort rather than outright edge. That positioning is part of why used values have held up reasonably well relative to how depreciation usually treats German performance sedans, and why the ownership math below matters more than the badge.

This Generation at a Glance

The B9 rides on Volkswagen Group's MLB Evo platform, an evolution of the outgoing B8's architecture rather than a clean-sheet redesign. The biggest change from the B8 S4 wasn't styling: it was underneath the hood. Audi swapped the B8's supercharged 3.0 TFSI for a single-turbo version of the same displacement, and retired the manual and DL501 dual-clutch transmissions in favor of a conventional ZF 8-speed torque-converter automatic. Every B9 S4 sold in the US came with quattro all-wheel drive as standard.

The generation splits cleanly into two halves. Cars built through 2019 use Audi's MIB2 infotainment system, sold at Premium Plus and Prestige trim (Premium joined the S4 lineup for 2019). The 2020 model year brought a mid-cycle refresh, unofficially called B9.5 by owners, with a revised grille, less angular headlights, a 10.1-inch touchscreen, and the MIB3 infotainment system that Audi says runs roughly ten times faster than MIB2. Standard LED headlights arrived across the line for 2020. The engine and transmission carried over unchanged through the refresh and to the end of production in 2024.

Every B9 S4 runs Audi's quattro all-wheel-drive system with a standard open rear differential, though the optional sport rear differential is worth seeking out on a test drive: it actively vectors torque side to side under load and noticeably sharpens corner exit compared to the base setup. Unlike the previous B8 generation, there's no wagon, coupe, or convertible body style tied to the S4 name; those variants live under the S5 badge on the same MLB Evo platform, sharing the engine and much of the chassis hardware but not the sedan-specific body-in-white.

Current pricing and inventory: Audi S4 market data, with per-year pages for 2018, 2019, 2020, 2021, 2022, 2023, and 2024.

Powertrain & Trim Breakdown

3.0 TFSI Turbo V6 (EA839): Every B9 S4

Owners consistently praise this engine for how usable its power is. The 349 hp and 369 lb-ft arrive earlier in the rev range than the outgoing supercharged unit managed, and the ZF 8-speed shifts smoother and holds up better under daily use than the B8's dual-clutch box. That's the good news. The bad news is generation-defining and shows up on forum threads with titles that don't leave much to the imagination.

What owners on Audizine's B9 reliability threads consistently cite as the car's strength is how little compromise it asks for day to day: quattro grip in bad weather, a torque curve that doesn't need to be revved out to feel quick, and a cabin quiet enough that the turbo V6 fades into the background on a highway commute. The tradeoff for that composure is a car that some owners describe as numb compared to a manual B8 S4 or a rival BMW, a fair complaint from people cross-shopping on feel rather than outright pace.

Rocker arm failure. Early production EA839 engines, concentrated in 2018 and some early 2019 builds, are prone to rocker arm failure. Audizine and AudiWorld both host long-running dedicated threads on the issue. The failure starts as a loud tick, distinct from the normal injector or high-pressure fuel pump clatter these engines make, and if driven through, it can take the camshaft and lifters with it. Because the rocker arms sit under the cam cover, the repair is an engine-out job. Forum-reported bills run $5,000 and up at independent European specialty shops, more at a dealer. Audi never issued a recall. Owners report the automaker has offered goodwill assistance on cars still within roughly five years of the original sale, but that's discretionary, not guaranteed. Audi revised the rocker arm design, with a larger roller bearing, partway through the B9's production run. There's no single clean year cutoff owners agree on, which is exactly why a cold-start listen during your test drive matters more than checking a VIN against a model year.

Timing chain tensioner wear. The EA839's tensioners can wear enough to let the chain rattle, producing a metallic, diesel-like clatter for one to five seconds on cold start before oil pressure builds and it quiets down. Forum reports place failures anywhere from the 20,000-mile mark on early or hard-driven examples out past 70,000 miles on cars that hold up well. Blackforesttechnik, a European specialty shop, documented a full tensioner and chain replacement on an 86,000-mile S4. Repair costs run up to $3,700 depending on whether the tensioner alone needs replacement or the full chain and guides do. Revised tensioners fitted later in production appear to hold up better based on high-mileage threads on Audizine, but there's no way to confirm which revision is in a specific car without pulling it.

Water pump and PCV failures. Both are wear items on this engine rather than defects. Water pumps have been reported failing around the 100,000-mile mark, with parts and labor running up to $1,400. PCV and valve cover failures, which show up as oil smell, rough idle, or a check engine light, run up to $1,300 to correct.

MIB2 infotainment freezing (2018-2019 cars only). Pre-refresh S4s running MIB2 are prone to the screen and virtual cockpit freezing or going black mid-drive, then rebooting on their own. It's a firmware issue shared across the B9-generation A4, A5, and Q5, not unique to the S4. Owners report holding the volume knob and top-left menu button for about ten seconds forces a manual reboot, and dealer firmware updates have resolved it for many owners. If resets stop working, an MMI control unit replacement runs $500-$1,200 plus programming. Cars built from the 2020 refresh onward use MIB3 and don't share this issue.

Carbon buildup. Like most modern direct-injection engines, the EA839 doesn't wash fuel across the intake valves, so carbon accumulates over time. Specialty shops recommend a walnut-blasting intake cleaning around every 60,000 miles to keep it from affecting idle quality and throttle response.

Suspension bushings. Front control arm bushings wear out earlier on the B9 than on most competitors in this class. It's not expensive to fix, but it's common enough that a pre-purchase inspection should specifically check for clunks over bumps and uneven front tire wear.

Trim Levels

Two things matter more than the trim badge on the trunk lid. First, exactly which features live in which trim shifted during the run: some Prestige-exclusive items on early cars, like adaptive cruise, moved down into Premium Plus on later ones. Don't assume a 2018 Prestige and a 2023 Premium Plus have the same options list; check the window sticker or build sheet for the specific car. Second, Audi didn't offer Premium as an S4 trim until the 2019 model year, so any 2018 car you find will be Premium Plus or Prestige.

Options worth seeking out regardless of trim: the sport rear differential, which meaningfully sharpens turn-in and corner exit compared to the standard open rear diff, and the Black Optic package, which swaps chrome trim for gloss black. Neither affects reliability, so they're purely a taste call.

None of the trim or package choices change which engine, transmission, or wheel size you get; every B9 S4 shares the same 349-hp drivetrain regardless of trim. That makes trim shopping mostly a question of which convenience and safety features you want standard versus which you're willing to live without, not a performance decision. If resale value matters to you down the line, Premium Plus tends to be the easiest trim to move because it covers the features most buyers search for (adaptive cruise, the digital gauge cluster) without the price premium of Prestige's audio and steering upgrades.

Which Year Should You Buy?

CarScout's NHTSA-sourced data shows no recalls logged against the B9 S4 for any model year 2018 through 2024. That's not the same as a clean bill of health: it just means nothing has been filed as a formal safety recall, as opposed to the rocker arm and timing chain issues above, which owners and Audi have handled through goodwill repairs and TSBs rather than recall campaigns. Run any VIN you're serious about through CarScout's recall lookup tool before you buy, since recall filings can post after a car changes hands.

The 2020-2024 refresh cars are the sweet spot. You get the same 349-hp engine and 8-speed automatic as the launch cars, the faster and more reliable MIB3 infotainment, and you're buying past the point where most rocker arm failures would have already surfaced under a previous owner's warranty. A 2018 or 2019 car isn't a car to avoid outright, since plenty have covered 80,000-plus miles with no rocker arm or timing chain drama, but it's a car that needs a cold-start listen and full service history before you commit.

Pre-Purchase Inspection Checklist

• Start the car cold, before it's been driven that day. Listen for a metallic, diesel-like rattle from the front of the engine that fades within a few seconds as oil pressure builds. That's the timing chain tensioner signature. A loud, persistent tick that doesn't fade is more consistent with a rocker arm problem. Either one is a reason to walk or renegotiate, not a reason to buy and hope.
• Ask for full service records, specifically oil change intervals. This engine is unforgiving of stretched oil change intervals; VW Group's 508.00-spec synthetic oil and consistent 10,000-mile service matter more here than on a typical family sedan.
• Check for any rocker arm or timing chain work already done. A car with a documented rocker arm replacement, or one with a tensioner already swapped to the revised part, is arguably safer to buy than an unknown 2018 with no records, because the expensive failure has already been dealt with.
• Test the infotainment screen and virtual cockpit for freezes or black-screen reboots, especially on 2018-2019 cars running MIB2. Cycle through nav, media, and the digital gauge cluster during your test drive rather than just glancing at the screen in the lot.
• Drive over a rough patch of road and listen for clunks from the front end. Worn front control arm bushings are common on this platform and cheap compared to the engine issues above, but they're a useful negotiating point.
• Have a PPI shop check for oil seepage around the valve cover and PCV system, and smell for a faint oil odor at idle, both early signs of PCV or valve cover failure.
• Ask when the water pump was last replaced, particularly on cars past 90,000 miles. It's a wear item on this engine, not a defect, but it's worth knowing whether it's already been done.
• Check for carbon buildup symptoms: a rough idle or hesitation off the line can point to an intake that's never been walnut-blasted. Ask for service records showing the car's mileage against the roughly 60,000-mile cleaning interval.

Running Costs

Fuel economy and routine maintenance intervals are ordinary for a performance sedan in this class. The number that actually separates a cheap ownership year from an expensive one is whether the car you're buying has already been through the rocker arm and timing chain failure window without an issue, or whether it's still ahead of you.

Budget for tires and brakes like you would on any AWD performance sedan riding on staggered summer or all-season rubber: expect to replace all four tires more often than on a comparable non-performance sedan, since quattro wears tires evenly but the factory performance compound doesn't last as long as a touring tire. Independent shops generally beat dealer labor rates by a wide margin on the wear items in the table above; the engine-specific repairs (rocker arm, timing chain) are worth getting quoted at both a dealer and a trusted European specialty shop before you commit to either.

FAQ

Is the Audi S4 B9 reliable? It's reliable in the sense that catastrophic engine failure isn't common, but early 2018-2019 cars carry a well-documented rocker arm failure risk that can mean a $5,000-plus repair. Buy a car with clean service records or one where that repair has already been done, and reliability concerns drop significantly.

What year Audi S4 should I avoid? No single year is a hard no, but 2018 and early 2019 cars have the highest concentration of rocker arm failure reports on Audizine and AudiWorld. That doesn't rule them out; it means you need a cold-start listen and full service history before buying one.

How many miles does a B9 Audi S4 last? Owners on Audizine's high-mileage thread report 100,000-plus miles with no major issues when maintenance, especially oil changes on VW Group's 508.00-spec oil, stays on schedule. The engine's failure points cluster in specific components rather than general wear-out, so a well-documented service history matters more than odometer mileage alone.

Is the 2020 refresh Audi S4 worth the extra money over a 2018 or 2019? For most buyers, yes. The 2020-and-later cars share the same engine and transmission but run the faster, more stable MIB3 infotainment system instead of the freeze-prone MIB2, and they're past the point where a previous owner would likely have already surfaced a rocker arm problem under warranty.

Does the Audi S4 B9 need premium fuel? Yes. The 3.0-liter turbo V6 is tuned around premium fuel and its EPA fuel economy ratings, 21 city, 30 highway, 24 combined, assume it. Running lower-octane fuel regularly can trigger knock retard and cost you both power and efficiency, so it's not a place to cut corners on running costs.

The Bottom Line

A 2020-2024 Audi S4 with documented service history is the easy recommendation here: same 349-hp turbo V6 and 8-speed automatic as the launch cars, better infotainment, and less rocker arm risk hanging over it. A 2018 or 2019 car isn't automatically a bad buy, but it needs a cold engine start, a full look at service records, and ideally evidence that the rocker arm or timing chain work has already been done by a previous owner. Always run the VIN through a recall check before you commit. CarScout members can set up scouts to track specific trims and years across the used market at usecarscout.com, with results delivered as a daily digest email rather than a live feed.

Sources: Audizine and AudiWorld B9 platform forums, ThreePiece.us, Alex's Autohaus, Blackforesttechnik, RepairPal, CarParts.com, FCP Euro, JXL Performance, Euro Premium Parts, Edmunds, Kelley Blue Book, JD Power, Cars.com, CarBuzz, Wards Auto, Motor1, Fuelly, CarEdge, and EPA fuel economy data via fueleconomy.gov, cross-checked against CarScout's NHTSA-sourced per-year market data.