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

# Powertrain Research Method

## Exact identity first

Resolve engine and transmission before assigning risk. Model-year cutovers, build-date revisions, market-specific engines, and optional transmissions can completely change the answer.

Classify the vehicle before researching it:

- internal-combustion engine (gasoline or diesel)
- mild hybrid
- full hybrid
- plug-in hybrid
- battery electric vehicle (BEV)

Record:

- engine code/family
- displacement/aspiration
- fuel system
- transmission, transaxle, e-CVT, or reduction-gear code/family and type
- electric motor/drive-unit family when applicable
- traction-battery chemistry/pack family and usable capacity when applicable
- onboard charger, DC fast-charge architecture, and thermal-management design when applicable
- AWD/4WD system when relevant
- production/build date if revisions matter

## Engine risk card

For every material engine issue, record:

- issue
- affected range
- evidence strength
- common trigger/onset pattern
- symptoms
- consequence
- prevention/updated part
- repair cost range
- PPI detection method
- purchase implication

Rate severity:

- 1: nuisance / inexpensive
- 2: moderate repair
- 3: expensive but manageable
- 4: major four-figure failure
- 5: engine-damaging or economic-total risk

Rate evidence:

- A: manufacturer/regulator/large robust dataset
- B: repeated specialist/technical evidence
- C: repeated owner pattern with partial technical support
- D: anecdotal/uncertain

Do not turn evidence grade into a fake failure percentage.

## Transmission, drivetrain, and electrified-powertrain risk card

Apply the same framework separately to:

- conventional automatic
- CVT
- dual-clutch/DCT/SST
- manual gearbox/clutch/DMF
- transfer case
- center differential/AWD coupling
- front/rear differentials
- electric motor/drive unit and reduction gear
- inverter, DC-DC converter, onboard charger, and charge port
- traction battery, battery-management system, thermal management, and high-voltage safety system
- regenerative braking and hybrid power-split/e-CVT system

For DCT/CVT/e-CVT/complex AWD systems, service history can materially affect risk. Verify interval,
fluid specification, software updates, and evidence of service. For EVs and hybrids, do not substitute
an advertised driving range for a battery-health test; obtain state-of-health, fault-history, charging,
and cell-balance evidence where possible.

For every expensive subsystem, search the manufacturer and the relevant regulator for recalls, service
campaigns, technical bulletins, warranty enhancements, and coverage extensions. Treat those findings as
evidence to investigate—not proof that every vehicle has the defect—and verify applicability by VIN,
market, build date, in-service date, mileage, and transfer rules.

## Serviceability-trap card

For every engine, transmission, transaxle, and drive unit, record:

- whether the unit is actually serviceable, rebuildable, or treated as a sealed assembly
- manufacturer fluid/filter inspection and replacement procedure; do not equate "lifetime fill" with zero degradation
- fluid specification, fill-level procedure, adaptation/relearn requirements, and special diagnostic tools
- access difficulty: engine-out, transmission removal, subframe drop, battery-pack removal, or major disassembly
- parts availability, specialist/dealer dependence, labour hours, and whether a failed unit is replaced rather than repaired
- unusual architecture that creates maintenance exposure: wet timing belt, rear-mounted timing chain,
  internal water pump, integrated exhaust/cooling module, oil-pump belt, high-pressure fuel system,
  dry-sump or complex scavenge system, non-serviceable hybrid transaxle, or proprietary EV drive unit

Flag a serviceability trap even when the component is currently functioning normally. Price the likely
scheduled service separately from the low-probability replacement tail risk.

## Dynamic lubrication and oil-starvation card

For sports cars, high-output engines, turbocharged engines, and vehicles the buyer may drive hard, research:

- wet- versus dry-sump layout, oil capacity, baffling, windage control, pickup design, and oil-cooler capacity
- documented oil-pressure drops, bearing/rod failures, pickup uncovering, or lubrication-related recalls/bulletins
- sustained lateral-G, hard-braking, acceleration, and track-use behaviour from technical or track-focused sources
- factory track-maintenance guidance, oil-level sensitivity, approved oil grades, pressure sensors, and logging capability
- whether an aftermarket baffled pan, accusump, cooler, or revised pickup is a proven preventive update or merely anecdotal

If evidence is incomplete, say so explicitly. Do not infer high-G lubrication safety from normal commuting,
a clean idle, or the absence of a dashboard warning.

## Revision handling

If an issue was revised mid-production:

- identify the revision date/part number if reliable evidence exists
- determine whether the candidate predates or postdates it
- do not assume a repaired pre-revision car received the updated design
- request invoice/parts detail when that distinction matters

## Modification handling

Map modifications to added stress:

- ECU tune / boost increase
- intake/exhaust changes
- turbo/supercharger upgrades
- transmission tune
- launch-control use
- lowered suspension
- wheel/tire changes
- emissions-system removal

A modification is not automatically bad. Judge tune quality, supporting modifications, service history, drivetrain torque margin, inspection legality, and documentation.