2017 BMW 420 2.0L Diesel · LB66 UFD

Fuel economy for the 1995cc 420d is generally in the 50–60 mpg range on a long run, dropping to around 35–45 mpg in mixed or urban driving — typical for this engine. As a diesel registered February 2017, it sits in Vehicle Excise Duty band G if list price was over £40,000 originally (the 4 Series range typically was), meaning a £210 supplement for the first five years has already expired, leaving standard £35 annual tax. Insurance for a 4 Series coupe typically falls in groups 30–34, so expect premiums in the £700–£1,100 region for a typical driver.

Maintenance costs are where this car warrants caution. BMW servicing at a franchised dealer is expensive, but specialists can service the 420d for £200–£350 depending on whether it is an interim or full service. Common ageing items include brake discs and pads (rear around £250, front £300), tyres (premium run-flats around £150 each), and timing chain service intervals which can be a four-figure job. Based on the mileage and emerging advisories, budget realistically for higher-than-average maintenance in the next 12–24 months.

Start with a physical inspection of the steering — with the engine running and the front wheels off the ground (or on a ramp), check for any clonking or play through the steering rack by hand. The advisory confirms play exists; you need to assess whether it is at the early or late stage. Also turn the wheel lock-to-lock and listen for whining, which suggests rack wear beyond just the inner joint. Ask for a printout from a BMW diagnostics tool (ISTA) if possible to check for any steering-related fault codes.

For the noisy rear differential flagged in 2025, a road test is essential. Listen from cold and warm, both at idle and under gentle acceleration — the noise should change character. Also check the underside for any signs of diff oil leaks (a common early indicator before the noise worsens). Inspect the rear tyres for uneven wear, which can indicate diff issues. Beyond these specific concerns, check the B47 diesel engine for any signs of timing chain stretch (rattling on cold start), inspect the EGR valve and intake for carbon build-up (common on high-mileage 420ds), and verify that all four tyres are matching in brand and tread depth.