Every number on this site is traceable, tagged, and verifiable. This page explains our data sources, our verification process, and how we ensure the figures we publish are accurate and trustworthy.
We are an independent editorial resource, not a garage. Every number on this site is traceable, tagged, and verifiable. This page explains our data sources, our verification process, and how we ensure the figures we publish are accurate and trustworthy.
[EM-VERIFIED], [EM-QUOTE], [PATTERN DATA], [THIRD-PARTY], [EM-INTERVIEW], [EM-SURVEY]Full methodology, data sources, tagging rules, and our commitment to transparency, below.
We publish only what we can verify. Our data comes from four primary sources, each with its own verification standard.
1. Proprietary enquiry data. We analyse quote requests submitted through EnginesMarket.co.uk and EngineFinders.co.uk. This is our single largest source, with 24,650 unique quote requests in 2025 [EM-VERIFIED]. This data gives us real-world volume, model distribution, and condition preferences.
2. Supplier quote data. We aggregate actual quotes sent to customers via our CRM, cross-checked against marketplaces like eBay Motors and PistonHeads. This produces our cost ranges, tagged [EM-QUOTE].
3. Specialist interviews. We conduct ongoing interviews with 100+ UK engine specialists, gathering qualitative insights on failure patterns, repairability, and preventative actions. Tagged [EM-INTERVIEW] and [EM-SURVEY] where appropriate.
4. Third-party sources. Manufacturer Technical Service Bulletins (TSBs), Auto Trader valuations, and other named sources, tagged [THIRD-PARTY]. We always cite the specific source and date.
Our full methodology is published separately, with detailed explanations of sample sizes, data cleaning, and limitations.
Every number on this site carries exactly one of six tags. A number with no tag is a build failure and does not publish.
| Tag | Meaning | Source |
|---|---|---|
[EM-VERIFIED] | Exact count or percentage from our internal CRM (enquiry volumes, model requests, condition split) | 24,650 quote requests, Jan–Dec 2025 |
[EM-QUOTE] | Pricing ranges derived from actual supplier quotes sent through our CRM, cross-checked with marketplaces | Supplier quotes + interviews |
[EM-INTERVIEW] | Direct statements from mechanics, workshop owners, or supplier managers | Hundreds of conversations 2024–2025 |
[EM-SURVEY] | Post-sale customer survey results (e.g., satisfaction rates) | 100+ surveys 3–6 months after replacement |
[THIRD-PARTY] | External data (Auto Trader, Parkers, manufacturer TSBs, etc.) | Named source + date |
[PATTERN DATA] | Documented expert-knowledge-tier claim, no proprietary volume behind it | Workshop consensus / market observation |
We never mislabel a [PATTERN DATA] figure as [EM-VERIFIED]. Doing so would undermine every verified number on the site. Our editorial standards and corrections log provide additional accountability.
Four steps. Every figure. Every time.
[EM-QUOTE] cost range is checked against eBay Motors and classified ads.If a number cannot be sourced or tagged, it does not appear on the site. We use [PLACEHOLDER] only during the draft stage; these are removed before publishing. Our editorial standards set out the full policy.
We use third-party data where it adds value, but we always source and date it.
Vehicle value bands on this site are derived from AutoTrader, AutoUncle, CarGurus, and Cazoo UK market data for 2025, tagged [THIRD-PARTY]. We do not rely on third-party data alone — we cross-reference with our own enquiry data and specialist interviews.
Manufacturer TSBs and recall information are also sourced from third parties (e.g., BMW AG, DVSA) and tagged [THIRD-PARTY] with the specific TSB number or recall reference. We always cite the source and date.
Where third-party data is updated or corrected, we update our pages and log the change in our corrections log.
Data drives every editorial decision on this site — from reliability ratings to repair-recommendations.
Reliability ratings. Every reliability rating, star rating, and Engine Score is inherited verbatim from the relevant Engine Knowledge Centre. These are never re-derived on a variant or model page. The Knowledge Centre itself bases its rating on the triangulated data sources above.
Repair-vs-replace decisions. Our repair vs replace framework applies the 70% threshold (for BMW) — a figure derived from the cost data we have collected and verified. If the lowest viable replacement cost exceeds 70% of the vehicle's current market value, we recommend evaluating scrap first.
Enquiry volumes. We never use enquiry volume as a proxy for failure rate. A high enquiry count (e.g., N47D20C with 1,450 requests [EM-VERIFIED]) reflects market demand, not engineering quality. We always pair volume data with qualitative failure patterns from the [PATTERN DATA] and [EM-INTERVIEW] tags.
Our annual failure index and per-engine data pages are the clearest expression of this approach.
We publish our methods, our mistakes, and our corrections.
Methodology. Our published methodology sets out sample sizes, data cleaning processes, and limitations in full. This is non-negotiable and never buried.
Corrections. If we get something wrong, we correct it and log it. Our corrections log is a permanent public record of every substantive change we have made.
Editorial standards. Our editorial standards page sets out our values, our independence, and our accountability to the data.
Vetting. Our specialist vetting process is also published — because the data we use comes from real specialists, and you deserve to know how we select them.
We are not a garage, we are not affiliated with BMW AG, and we do not sell engines. We research, verify, and route. That is the whole job.
It means the number is an exact count or percentage from our internal CRM data — 24,650 quote requests in 2025. We never round or approximate these figures.
We cross-reference specialist claims with our proprietary enquiry data, third-party TSBs, and at least one other source. Claims marked [EM-INTERVIEW] are direct quotes from verified specialists.
No. Our data is sourced from real enquiries, real quotes, real interviews, and real third-party sources. We do not use AI to invent or extrapolate numbers.
We cite third-party data with the source and date, and we cross-reference it with our own data. It is one input among several, not the sole basis for any recommendation.
We update the affected page, log the change in our corrections log, and where relevant, add a correction notice to the page itself.
Every Number Tagged A figure with no tag does not publish. Period.
Sources Published We tell you where every number comes from — not just "proprietary data".
Corrections Logged Mistakes are corrected and logged publicly. No hidden edits.
Not a Garage We research and route. We never claim to do the work.
Explore our engine data pages, failure indexes, and economics guides — all built on verified numbers.
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