The W177 A45 S is a high-output hatchback that rewards a careful inspection. Prioritise documented servicing, matched tyres and clean operation of the transmission and AWD system. Get any drivetrain warning diagnosed before assuming it needs only a fluid change.
Which Mercedes-AMG A45 S W177 should you buy?
Mercedes-AMG’s A-Class model page identifies 310 kW (421 PS) and AMG SPEEDSHIFT DCT 8G. The S uses 4MATIC+ with rear torque distribution. Keep the older W176 and A35 separate when comparing prices. Verify the actual equipment, year, aero package, dampers and wheels.
UK asking prices
On 6 November 2026, PistonHeads showed a 2020 A45 S at £29,499 with 48,111 miles and a 2025 A45 S Plus at £46,490 with 7,200 miles. These are asking prices. Compare the same age and trim and get quotes for any deferred work.
Common problems and inspection points
M139 engine, cooling and tuning
Start cold and inspect fluids, the cooling stack and visible hose joints. Ask about repeated top-ups and have unexplained loss investigated. Drive fully warm and check boost and warning history. Request tuning and hardware invoices, fuel requirements and insurance acceptance for the actual setup.
DCT and 4MATIC+
Check cold engagement and warm parking manoeuvres and gentle shifts. Have repeatable shunting or drivetrain warnings scanned. Ask for separate gearbox and rear-drive invoices and verify fluids and schedule for the build. Check tyre sizes and rolling circumference and inspect rear hardware and seals on a lift.
Brakes, suspension and technology
Inspect inner disc faces and tyre shoulders, test braking and check the adaptive suspension if fitted. Test MBUX, driver assistance, lights and cameras. Ask whether sensors were recalibrated after glass or bumper repairs. Look for damage at the cooling stack, jacking points and undertrays.
Maintenance and parts
The M139 uses a timing chain and separate accessory drive. Confirm the Mercedes oil approval, transmission and rear-drive service requirements by VIN. Match brakes and filters to the fitted equipment.
Affiliate disclosure. We may earn a commission on purchases through the eBay links below. These are indicative UK parts-only allowances. Confirm the OE number and get fitted quotes separately.
| Part | Allowance | Fitment check |
|---|---|---|
| Oil service kit | £70–£155 | Match Mercedes approval. |
| Spark plugs | £55–£140 | Check engine and tune. |
| Ignition coils | £40–£105 | Diagnose first. |
| Alternator | £175–£470 | Verify OE number. |
| Accessory belt | £50–£145 | Check routing. |
| Air filter | £20–£65 | Check airbox. |
| Front pads | £85–£220 | Match caliper. |
| Front discs | £280–£720 | Verify rotor package. |
| DCT service parts | £110–£270 | Match transmission. |
| Rear drive fluid | £40–£105 | Identify exact unit. |
| Cabin filter | £15–£48 | Verify housing. |
Hidden ownership costs
Price tyres, brakes and adaptive dampers before comparing offers. Obtain a specialist diagnosis for any unresolved DCT or AWD symptom. Budget for fuel and insurance on the actual registration and for any work needed to restore missing standard hardware.
Viewing checklist
- Confirm VIN, W177 S specification and options.
- Start cold and drive fully warm.
- Check brakes, tyres, damping and drivetrain warnings.
- Review dated servicing and tune invoices.
- Check MOT history and obtain written repair estimates.
Mercedes-AMG A45 S W177 FAQ
Is this the same as the W176 A45?
The W177 A45 S has its own M139 and drivetrain specification. Compare generations separately.
Does the A45 S use an automatic?
It uses AMG SPEEDSHIFT DCT 8G.
Can I value a car with a drivetrain warning?
Get the actual fault diagnosed and a written fitted repair quote first.
