Sources & Editorial Standards

Public data sources

• DVLA Vehicle Enquiry Service — UK registration → factory spec (make, model, colour, first-registered, MOT due, tax status, emission class, CO₂, fuel type). Open Government Licence. Integrated at our Worker API, surfacing in the app's reg-lookup flow.
• DVSA MOT History API — per-registration MOT history including mileage at each test, advisories, and failures. Open Government Licence. Integrated at our Worker API; frontend integration in progress.
• gov.uk/check-vehicle-recall — authoritative UK recall lookup. We prompt users to verify recalls with the VIN rather than claiming completion status ourselves.
• Wikipedia engine pages — BMW_N47, BMW_B47, BMW_N57, BMW_B57, BMW_B58, BMW_S55. CC-BY-SA, cited for historical specification context.
• BMW press archives — manufacturer spec sheets, UK launch press, BMW Technology Office technical articles. Used for chassis × engine mapping and authoritative emissions/ULEZ classifications.
• UK trade press — Autocar, Car Magazine, What Car, PistonHeads Test Drives. Used for launch-year fact-checking and market-context.

Failure-pattern sources

• DVSA advisory aggregates — rolled-up MOT advisory data by engine/chassis cohort, sense-checked against forum consensus.
• Independent BMW specialist maintenance schedules — typically more cautious than BMW's factory schedule (especially oil intervals). Drawn from BMW CCA's technical library and independent UK specialist publications.
• Forum consensus threads — Bimmer Post (F30 320d, F10 520d, F25 X3 20d, M140i, M3 F80), Bimmerfest, PistonHeads BMW sections. We link to threads when citing consensus; we do not copy user content into our database.
• Recall database cross-reference — DVSA recall records (UK) and NHTSA (US) cross-referenced for shared failure modes across markets.

What we don't use

• AI content farms — bimmerboom.com, similar sites generating machine-written BMW "guides" at scale. Using them compounds errors.
• Competitor-scraped content — we don't ingest HPI Check reports, Carfax content, or any paid-vendor data we don't have rights to.
• Fake or fabricated user reviews — if we publish testimonials, they'll be real.
• LLM general knowledge for factual claims about engines — we've tested this and it hallucinates engine codes confidently. All our engine-level facts come from the structured reference tables, not the model.

Editorial review

• Public SEO content — this page, the engine guides, the pre-purchase inspection checklist, and the HPI comparison — is hand-written and reviewed before publication.
• Engine-failure database records are reviewed against at least three independent sources before addition. Each failure mode lists its severity, frequency, mileage onset range, UK cost range, and — where applicable — the recall or TSB reference.
• Cost ranges are verified against at least two UK independent specialist quotes per failure mode. Where we're uncertain we say "typical range" and note the variables that move the cost.

Correction handling

Spot an error? Email [email protected] with:

• The page URL
• The specific claim that's wrong
• A source or reasoning for the correction

We review corrections within 7 days and publish visible update notes with the date. No contact ignored — we'd rather ship a correction than leave a stale page live.