Compare the cost of completing the same repair, not the parts sticker alone
An imported-car owner replacing an electric water pump, steering assembly, climate-control module, or another expensive component may see a large headline gap among genuine or OEM, aftermarket-new, and remanufactured parts.
The installed bill can also contain freight, import duties and taxes, removal and fitting labor, diagnosis, coding, calibration, consumables, and a refundable core charge.
If the symptom returns, a warranty that replaces the part but excludes removal labor, programming, freight, or vehicle downtime can leave a substantial second bill.
The lowest part price is therefore not automatically the lowest economic cost over the period you intend to keep the vehicle.
This calculator aligns three written quotes to one diagnosed repair scope and places initial cash, core refunds, probability-weighted rework, expected warranty recovery, downtime, and end-of-horizon resale adjustment on a common timeline.
Future costs use your escalation and discount assumptions, while break-even outputs show the rework probability or initial labor amount that would make an alternative equal to the OEM case.
It does not rank durability or safety, identify compatible parts, approve a warranty claim, or recommend a seller.
Confirm the vehicle identification number, exact part reference, manufacturer, condition, installation suitability, and written coverage before treating any quote as decision-ready.
Loss to avoid
Choosing a low part price while omitting freight, taxes, fitting, coding, repeat repair, core risk, and downtime
Decision to confirm
How three like-for-like repair options compare on 36-month present-value economic cost and downside tolerance
Next action
Request matched written quotes with VIN, part number, labor coverage, and core-return terms
Treat OEM, aftermarket, and remanufactured as quote labels, not quality verdicts
The term OEM may describe a genuine part in the vehicle-maker package, a separately distributed item from an original-equipment supplier, or merely a seller's claim that a product is equivalent.
Aftermarket-new products range from independently certified replacement parts to products carrying no relevant certification claim.
Remanufactured units can differ in replaced subcomponents, test procedure, traceability, core acceptance, and the party that stands behind the warranty.
The three input columns are organizational labels only and do not turn marketing language into a legal category or technical conclusion.
Evidence to match and conclusions excluded for each parts option| Input option | Record from evidence | Not decided by the calculator |
|---|
| Genuine or OEM | Package brand, actual manufacturer, part number, new condition, and supply channel | That genuine and OE-supplier distribution are identical |
| Aftermarket new | Independent manufacturer, part number, certification marking, and VIN-fit evidence | That every aftermarket item is certified or genuine-equivalent |
| Remanufactured | Rebuilder, replaced scope, test evidence, core return, and warranty administrator | Remaining life or safety and quality superiority |
Verify safety-critical suitability before comparing price
Braking, steering, restraint, and high-voltage components require special attention to VIN fit, applicable certification, manufacturer procedures, software compatibility, and technician capability.
An unsuitable component is not a valid low-cost option, so leave its compatibility confirmation unchecked.
A seller's vehicle-name listing is not a substitute for matching superseded part numbers, connectors, control-unit versions, and required calibration.
Build a like-for-like comparison in six passes
- Freeze one repair scope. Record the diagnosed fault, every component and quantity, surrounding consumables, diagnostic work, calibration, and road test.
- Identify each part. Copy the manufacturer, exact reference, new or remanufactured condition, certification marking, and rebuild organization from evidence.
- Separate cash lines. Enter the part, freight, duties and taxes, fitting labor, diagnosis and coding, other confirmed charges, and core deposit without duplication.
- Split warranty coverage. Confirm whether coverage pays for the replacement component, removal and fitting labor, diagnosis, coding, return freight, and transport.
- Model uncertainty explicitly. Treat rework probability, event month, future repair amount, downtime, and resale impact as scenarios rather than published facts.
- Open the evidence gate last. Confirm common scope and tax basis plus each quote, fit, warranty, technician suitability, and resale assumption before reading a confirmed leader.
Mixing a VAT-inclusive quote with a VAT-exclusive quote, or including preventive work in only one option, can create a precise-looking but meaningless ranking.
For an overseas purchase, the tool does not predict exchange rates or customs liability; enter the confirmed KRW card amount, freight, and import charges that apply to your transaction.
A core deposit is cash paid at installation, whereas the approved refund is a later inflow, so preserving both timing and amount reveals liquidity and rejection risk.
How the present-value economic TCO works
Core formulas
Quote total = part + freight + taxes + fitting + diagnostics/coding/calibration + other
Initial economic cost = quote total + core deposit + initial downtime days × daily value
Expected rework cash PV = probability × post-warranty-share rework cost × escalation factor ÷ discount factor
Expected downtime PV = probability × rework days × daily value ÷ discount factor
Economic TCO PV = initial economic cost − core refund PV + expected rework cash/downtime PV − terminal resale adjustment PV
If the expected event month falls inside the entered warranty term, the model subtracts only the separate parts and labor coverage percentages you supplied.
An event or core refund outside the selected horizon is excluded and produces a warning, making the boundary visible rather than silently pulling distant cash into the comparison.
A positive terminal resale adjustment lowers economic cost because it represents extra sale proceeds, while a negative adjustment raises cost.
Downtime is an economic value, not automatically a card payment, so do not count the same taxi, rental, or business interruption loss both there and under another cost line.
Expected warranty value
Probability-weighted present value of covered parts and labor when the event month is inside the entered term
Probability break-even
Alternative rework probability that equals the OEM economic TCO with every other assumption fixed
Labor break-even
Alternative initial fitting labor that equals the OEM economic TCO with future rework labor unchanged
Audit the formulas with the labelled synthetic example
The example button loads a fictional electric-water-pump scenario solely to validate behavior; it is not a quote, market average, brand failure rate, or parts recommendation.
It uses an 84-month-old vehicle at 110,000 km, a 36-month horizon, a 3% annual discount rate, 2% annual cost escalation, and KRW 100,000 per downtime day.
The OEM case uses KRW 2,400,000 parts plus KRW 800,000 fitting, coding, and other cost.
The aftermarket case uses KRW 1,420,000 of part, freight, and import charges plus KRW 800,000 fitting, coding, and other cost, while the remanufactured case uses KRW 1,000,000 plus KRW 850,000 and a core deposit.
Synthetic present-value results and OEM break-even thresholds| Result | Genuine/OEM | Aftermarket | Remanufactured |
|---|
| Present-value economic TCO | KRW 3,142,677 | KRW 2,865,648 | KRW 3,101,119 |
| Baseline rework probability | 6.00% | 15.00% | 25.00% |
| Probability break-even vs OEM | Not applicable | 27.02% | 27.01% |
| Initial fitting labor break-even | Not applicable | KRW 877,028 | KRW 691,558 |
Under those assumptions, the aftermarket result is KRW 235,471 below the remanufactured runner-up and KRW 277,029 below OEM.
All evidence confirmations deliberately remain off, so the example must stay locked as not ready even though a mathematical leader exists.
Raising aftermarket rework probability to about 27.02% with every other input fixed would erase its modeled advantage over OEM.
Reset the example before entering a real case so no fictional amount or risk assumption survives into your quote comparison.
Separate Korean statutory repair aftercare from contractual parts warranty
Article 58(5) of Korea's Automobile Management Act establishes duties around offering choices among new, used, and remanufactured parts, checking used or remanufactured parts, displaying labor information, issuing estimates and repair statements, and explaining aftercare.
Article 30-5 provides a performance and quality certification framework for replacement parts, but it does not mean every product entered in the aftermarket column is a certified part.
When a certification claim affects the decision, match the marking on the actual product and package against official vehicle-parts information and manufacturer documentation.
Article 134 of the Enforcement Rule, effective June 3, 2026 in the source checked for this calculator, contains 90-day, 60-day, and 30-day aftercare periods for failures caused by incorrect repair work.
The interface displays 90 days when vehicle age is under one year or mileage is no more than 20,000 km, 60 days when age is under three years or mileage is no more than 60,000 km, and 30 days otherwise.
That reference is not an automatic manufacturer, seller, or repairer warranty for every component failure and is never copied into the warranty inputs.
Preserve the estimate, repair statement, warranty document, part package, and communications, and obtain qualified advice if fault, coverage, or legal responsibility is disputed.
Primary verification paths
Model boundaries
- Prices, freight, taxes, and labor come only from the user's actual KRW quotes
- Rework probability is a scenario, not a reliability statistic supplied by MowaTool
- Discount and escalation rates are user assumptions for timing comparisons
- Fit, safety, certification, warranty approval, and liability are outside the calculation
Read sensitivity and break-even outputs as questions, not promises
Probability sensitivity halves, preserves, and increases the aftermarket and remanufactured probabilities by 50%, capped at 100%, while holding the OEM probability fixed.
If a lower-cost result loses its lead after a small change, evidence about failure exposure and labor warranty deserves more attention.
If the ranking survives a conservative probability scenario, the modeled cost margin is less sensitive to that particular uncertainty.
A missing break-even value means there is no crossing inside the valid 0% to 100% interval or no modeled event cost; it does not prove that the option carries no risk.
Horizon sensitivity compares 12, 36, and 60 months plus the selected horizon.
A near-term sale can make the terminal resale assumption more influential, whereas long ownership can include failures after short warranties expire.
Save separate cases for a delayed core refund, longer overseas lead time, rejected warranty labor, or more downtime instead of hiding all uncertainty in one probability.
When the modeled gap is small, traceable supply, verified fit, technician procedure, and enforceable coverage can reasonably matter more than the arithmetic ranking.
Practical scenarios
Official center genuine part vs specialist aftermarket part
Because both repair channel and part source change, first align diagnosis, equipment, coding, labor, and warranty responsibility, then record the remaining parts differences here.
Overseas new part vs domestic distributor
Include actual card conversion, freight, import charges, return cost, and arrival delay for the overseas case, while reflecting domestic lead time and claim access through downtime and coverage.
Core-return remanufactured unit
Add the deposit to initial cash and enter only the supportable refund and month after acceptance, preserving rejection and delay rather than assuming instant full recovery.
Repair shortly before vehicle sale
Use a resale adjustment only when a buyer, dealer, or comparable transaction supports it; otherwise keep the value at zero and document that neutral assumption.
Frequently asked questions
Is an OEM-labelled part always identical to a genuine part?
No. Trade usage varies. Verify the actual manufacturer, part number, condition, packaging, supply channel, and responsible warranty party rather than relying on the label.
Why does the calculator not provide an average aftermarket failure rate?
Brand, component family, application, production batch, and installation quality can differ too much for an unsupported average to be responsible. Compare several user-defined scenarios based on the evidence you can obtain.
Does an in-warranty rework event become completely free?
Not automatically. Parts and labor coverage are separate, and diagnosis, coding, freight, and downtime may remain excluded. Enter only the written percentages that apply.
What if the promised core refund exceeds the deposit?
Normalization caps the refund at the entered deposit. If the extra amount is a separate purchase payment or rebate, ask the supplier to clarify the quote instead of disguising it as a core refund.
Can I leave rework probability at zero when I do not know it?
Yes, but zero means a scenario that excludes expected failure cost, not proof of reliability. Compare low, baseline, and high cases and retain the warning in your interpretation.
Should I buy the option with the lowest confirmed TCO?
The output remains a cost comparison, not a purchase recommendation. Independently confirm safety-critical applicability, technician tools and procedure, supply traceability, and practical warranty enforcement.
Finish with a matched written quote sheet
Do not stop at a screenshot of the lowest result.
Ask each supplier to state repair scope, manufacturer and part number, condition, VAT, freight and import charges, fitting and coding, core acceptance, and separate parts and labor coverage in the same order.
Update the inputs from those documents, rerun the probability and horizon cases, and decide whether the cost difference is large enough to compensate for any remaining fit, safety, traceability, or enforcement uncertainty.
The legal-source review date is September 3, 2026, and the relevant Act text should be checked again after the later consolidated version's stated general effective date of December 17, 2026.
Present-value structure follows life-cycle-costing principles from NIST Handbook 135e2025 only; no U.S. public-facility discount rate or decision rule is imported into this Korean vehicle-repair model.