skills/used-car-investigator/references/maintenance.md

# Mileage and Maintenance Forecasting

## Build the timeline

Start from the manufacturer's schedule, then layer known model-specific preventive work and wear patterns.

For the candidate's current odometer, create four buckets:

1. **Overdue / undocumented now**
2. **Due within ~10,000 km**
3. **Likely within ~20,000-30,000 km**
4. **Material risk within ~50,000 km or the next 36 months**

Adjust the kilometre windows if the manufacturer uses shorter intervals or time-based service.

## Separate cost types

### Scheduled maintenance
Manufacturer- or specialist-supported recurring service.

### Wear item
Condition-dependent components such as tires, brakes, clutch, dampers, bushings, bearings, battery.

### Known failure-risk reserve
A recurring model-specific defect or expensive component with uncertain timing.

### Catch-up maintenance
Work that should have been performed but lacks evidence.

Never add all tail risks as though every one will occur. Show expected maintenance separately from catastrophic exposure.

## Documentation rule

If proof is absent, phrase it as:

"This service is due/expected by this mileage unless documentation shows it was completed."

Do not say it was skipped unless evidence shows that.

## Forecast math

When annual distance is known, forecast based on current mileage plus expected kilometres for 12/24/36 months.

When annual distance is unknown, use a disclosed generic scenario only if necessary for comparison.

For each interval, provide low/base/high where uncertainty is meaningful.

## Expensive-service watchlist

Always check applicability of:

- timing belt + tensioners + water pump
- timing chain/guide/tensioner risk
- clutch + dual-mass flywheel
- DCT/SST service and clutch/mechatronic risk
- CVT fluid and known valve-body/pulley issues
- sealed/lifetime-fluid transmission service procedure and replacement exposure
- conventional ATF/filter service
- differential/transfer-case fluids
- spark plugs
- valve adjustment
- coolant
- carbon cleaning
- turbo/supercharger service
- wet timing-belt oil specification, contamination, inspection, and replacement
- internal water pump, rear timing-chain, engine-out, and subframe-drop service exposure
- high-G oil starvation, oil-pressure monitoring, baffling, pickup, and oil-cooling requirements on performance cars
- suspension refresh
- wheel bearings
- brakes/tires
- tire type, tread depth, date code, matching, seasonal suitability, and AWD/4WD circumference matching
- rust remediation

## Cost location

Repair labour differs sharply by city and specialty. Use local currency and region where available. Distinguish dealer, specialist, and independent estimates when the difference is decision-relevant.