skills/used-car-investigator/references/research-and-sources.md

# Research and Source Hierarchy

Use current web research for every serious vehicle evaluation.

## Source priority

Prefer, roughly in this order:

1. Manufacturer owner's manuals, maintenance schedules, service campaigns, warranty extensions, and technical documentation.
2. Government VIN/recall/title resources applicable to the jurisdiction.
3. OEM parts/service information and recognized technical-service-bulletin databases where lawfully accessible.
4. High-quality independent reliability datasets and long-term fleet/inspection data.
5. Reputable marque specialists and independent repair shops with technically specific explanations.
6. Reputable automotive publications for instrumented tests and driving impressions.
7. Auction archives and historical marketplace listings for VIN/listing forensics.
8. Owner forums/communities for pattern discovery, then cross-check elsewhere.

Do not use a single forum post, TikTok, Reddit post, or seller claim as proof of a systemic defect.

For expensive powertrain concerns, explicitly search the manufacturer for warranty-enhancement programs,
coverage extensions, product campaigns, and technical-service bulletins. Report them separately from
safety recalls: they are evidence of a recognized condition or repair pathway, not proof that every car
will fail. Verify eligibility by VIN, jurisdiction, original in-service date, mileage, and transfer rules.

For hybrids and EVs, prioritize manufacturer battery-warranty terms, service campaigns, recall notices,
technical documentation, and a qualified battery-health diagnostic over range estimates, seller claims,
or forum anecdotes. Research battery state-of-health, usable-capacity loss, cell imbalance, thermal
management, charging hardware, high-voltage isolation, drive units, and warranty transferability.

For dealer experience, prioritize the written purchase order, warranty/CPO terms, fee disclosure, and
official licensing or regulator records. Use recurring public-review themes only as secondary signals;
do not treat a star average or one complaint as proof of misconduct.

## Canada

When applicable, prioritize Transport Canada for recalls and Canadian regulatory information. CARFAX Canada may contain accident/registration/lien/service information when the user supplies a report or lawful access exists. Do not imply a free public VIN search reproduces CARFAX Canada.

## United States

When applicable, use NHTSA/vPIC for VIN decoding and NHTSA recall information. Title-brand/lien access varies by state and service. Do not infer a clean title from NHTSA data.

## VIN searches

Search the complete VIN in quotes and unquoted forms. Look for prior listings, auction records, salvage images, cached snippets, mileage, trim, damage descriptions, and seller identity patterns.

Cross-check VIN-decoded attributes against the current ad:

- year
- plant/build information where available
- engine
- trim/series when decodable
- drivetrain
- body style

A mismatch is a red flag or a prompt for further verification, not automatic fraud.

## Repair costs

Use location-relevant cost evidence where possible. If exact current shop quotes are unavailable, provide a range and label the basis:

- parts + typical labour time estimate
- specialist-published estimate
- dealer estimate
- owner-reported invoice range

Do not present anecdotal invoice values as universal.

## Market pricing

Prioritize recent local comps. When using asking prices, explicitly call them asking prices.

For eBay Motors, sold/completed evidence is more useful than unsold asks when available. For Facebook Marketplace, AutoTrader, and Kijiji, account for seller type and listing age when visible.

## Driving dynamics

Use instrumented road tests and multiple reviews. Separate subjective impressions from measured acceleration/braking.

## Citation expectations

Cite the claims that most affect the purchase decision, especially:

- engine/transmission defect patterns
- service intervals
- recalls/service campaigns
- repair-cost estimates
- fuel requirement
- historical VIN/accident evidence
- fair-value comps
- acceleration/fuel-economy figures