Editorial and corrections policy

Source hierarchy

1. The manufacturer's own document — the owner's handbook, an official online handbook, a manufacturer specification page, or a manufacturer accessory fit list. Linked directly when it is public; named with the lookup link when it sits behind a VIN check.
2. A faithful mirror of the handbook (a scan or transcription of the printed book). Counts as a manufacturer source for verification but is never the link we show — the link goes to the manufacturer where one exists.
3. Owners'-club fitment lists and per-model retailer fitment pages, UK market only. Two independent ones agreeing verify a bulb or wiper row; one alone leaves the row marked likely.
4. Generic part finders, forums and US-market data — used to find candidates, never to verify. US-spec bulb charts in particular are wrong for many UK cars and are ignored.

The per-category bar (what verifies a bulb versus an oil spec) is on How we check.

How research is done, and how automation is used

Finding and reading handbooks for hundreds of cars is slow, so the research is done with AI-assisted tools that locate candidate documents, read the relevant pages and record the value, the source and the page reference. That is the collection step. Publication follows a fixed rule, not a judgement call: a row is marked verified only when the recorded source meets the hierarchy above for its category, and the source is stored against the row so it appears on the page.

A sample of cited sources is independently re-opened after each research pass to confirm the value really is on the page cited; the corrections that come out of those audits are applied to the database and noted on the affected rows. No sentence on a car page is generated at page-load time from a language model — every value, note and source you see is a stored record with a date.

The site's editor (Sean Turner, about) sets the verification rules, reviews audit findings and corrections, and is responsible for what is published.

Labels

Verified meets the rule for its category. Likely is the best value found from sources that do not yet meet it — shown because a good candidate is more useful than nothing, with the advice to check the part you remove. Unconfirmed on an engine oil page means we will not recommend a product for that engine yet. Pages with nothing verified are kept out of search engines until something is.

Corrections

Anyone can report an error from the button on every car page or via the contact page. Reports go into a queue and are re-checked against the handbook or the two-source rule. When a published value changes, the row keeps a note of what it was previously listed as and why it changed, and the page's “last checked” date moves. A handbook photo from an owner is the fastest way to close an unconfirmed engine.

We correct rather than quietly replace: if a value we published was wrong, the corrected row says so.

Independence and update cadence

Retailers and brands do not pay for placement, do not see pages before publication and cannot change a fitment. Affiliate links are labelled “Ad” (see the disclosure). Coverage is extended in batches; existing rows are re-checked when a report comes in, when a manufacturer document becomes available, and in periodic refresh passes for the most-visited cars.