How to Evaluate a Used Car

The CrappyCar Witch's Used Car Shield Charm & Checklist

Most buyers walk into a used car viewing without a plan. The seller knows exactly what they're showing you — and what they're not. The Shield Charm & Checklist is a one-page field guide for the on-the-ground check: the visual inspection, red flags to look for, and questions worth asking out loud, organized so you can work through it in real time with the car in front of you.

Open the Shield Charm & Checklist

Why a Pre-Purchase Inspection is Non-Negotiable

A vehicle history report tells you what happened. A mechanic's inspection tells you what's happening right now. These are different documents solving different problems — and only one of them will find the hairline crack in the exhaust manifold.

A pre-purchase inspection from an independent mechanic (not the selling dealer's shop) runs $100–$150 and puts the car on a lift. It will find deferred maintenance, hidden rust, oil leaks, suspension wear, and anything the seller hoped you wouldn't notice. If the seller refuses to allow an inspection, that refusal is the inspection result.

• Choose an independent shop — not affiliated with the seller
• Ask for a written report with estimated repair costs for any findings
• Enter that repair estimate into the Witch's pre-purchase inspection field — it replaces the baseline maintenance estimate for Year 1 with your actual number
• If findings are significant, re-run the analysis with those costs reflected before committing

What You Can Check Before Calling a Mechanic

You don't need a lift to gather evidence. Before you schedule the professional inspection, a careful walk-around takes 20 minutes and filters out cars not worth the inspection fee.

Exterior

• Rust on wheel wells, rocker panels, and frame rails — surface rust is cosmetic, structural rust is a different conversation
• Panel gaps — run your eye along the door seams and hood edges. Uneven gaps suggest prior collision repair or a bent frame
• Paint mismatch — look at the car from a low angle in daylight. Repainted panels reflect light differently
• Overspray on rubber trim, windows, or door jambs — confirms prior bodywork

Cold Start

• Insist on a cold start — if the seller has already warmed up the engine, ask why
• Blue smoke at startup: oil burning. White smoke that doesn't clear: coolant burning (head gasket concern)
• Rough or lumpy idle that smooths out: acceptable on many older engines. Rough idle that stays rough: investigate
• Any unusual knocking or ticking in the first 30 seconds

Under the Hood

• Oil dipstick: golden to dark brown is normal, milky or grey means coolant contamination — walk away
• Oil filler cap underside: light brown residue is fine, milky residue is not
• Coolant reservoir: should be green, orange, or pink — never brown or murky
• Belt condition: cracks, fraying, or glazing on the serpentine belt
• Fresh undercoating that doesn't match the car's age: potentially hiding rust or structural repair

Interior

• Musty or mildew smell: potential flood damage, even if carpets look clean
• Wear patterns inconsistent with mileage — a 40,000-mile car with a bald steering wheel hub raises questions
• Water stains on headliner or carpet edges
• All warning lights extinguish after startup — a cleared check engine light can return within a short drive

Reading a Vehicle History Report

Carfax, AutoCheck, and the NMVTIS database aggregate title history, reported accidents, odometer readings at service visits, and recall completion status. They are useful and incomplete in equal measure.

What it shows

• Title type — see below for what each means
• Number of previous owners and states registered in
• Reported accidents (insurance claims only — cash deals don't appear)
• Odometer readings at service visits — a car serviced at 12k, then 14k, then 47k has an unexplained gap
• Open recall status

Title types to know

• Clean: no known issues on record — the baseline
• Salvage: insurance declared it a total loss. Typically 20–40% below market, repair quality varies enormously
• Rebuilt/Reconstructed: was salvage, has since passed a state inspection. Resale value permanently impaired
• Lemon Law Buyback: manufacturer repurchased it under state lemon law. The problem that triggered the buyback may or may not be resolved
• Flood: the title that keeps giving. Electrical gremlins from flood damage can appear years after the event

What it doesn't show

• Accidents settled in cash — these never enter the insurance system
• Maintenance done privately or at independent shops that don't report to the database
• Flood damage from states or countries that don't mandate flood titling
• Mechanical condition — the report describes history, not current state

Red Flags by Category

These are the findings that change the math materially. Any one of them warrants either a hard negotiation on price or walking away entirely.

Using the Witch Alongside Your Evaluation

The CrappyCar Witch is designed to work with real inspection data, not despite it. The more specific your inputs, the more useful her output.

• Enter the mechanic's written repair estimate in the Pre-Purchase Inspection Quote field on the contender form — this replaces the baseline estimate for Year 1 with your actual number
• If the inspection finds deferred maintenance that wasn't in the asking price, re-run the analysis with those costs added
• Use the Curse Score alongside the inspection — a high complaint volume on a specific component category (e.g., engine) combined with an inspector finding early signs of that same failure is a meaningful convergence
• The ±20% uncertainty band on the projection chart is honest about what population averages can't see — a clean inspection narrows that band considerably on the downside
• If two contenders are within the margin of error numerically, the inspection quality of each becomes the tiebreaker