How the Scoring Works

Plain words, no black box. Here is exactly what gets counted, how the trouble index is built, and where it can mislead you.

Where the numbers come from

Three public files published by NHTSA's Office of Defects Investigation:

• Complaints — every report an owner files with the federal government (495,553 of them across the models covered here). These include the vehicle, what failed, whether there was a crash, fire, injury, or death, and often the odometer reading.
• Recalls — every safety recall campaign, with its remedy.
• Investigations — formal defect investigations, some of which lead to recalls.

The data refreshes from the source on an ongoing basis; the date at the bottom of every page says when the counts you're reading were last brought in line with NHTSA's file.

The trouble index

Every complaint counts once. A report gains extra weight when it involves a crash (+2), a fire (+3), an injury (+4), or a death (+8) — a transmission that strands you matters more than a rattle, and the index reflects that.

Each model year's weighted total is then scaled from 0 to 100 against the worst year of the same model. A 2013 Focus is scored against other Focuses, never against a Camry.

Why years are only compared within a model

Complaint counts have no denominator: NHTSA's file doesn't say how many of each car were sold, and a big seller will always out-complain a niche model regardless of quality. Comparing a year to its own siblings cancels most of that out. It's the honest comparison the data actually supports — so this site never claims "the Accord is more reliable than the Camry."

Verdicts

• Avoid — trouble index 55+, at least 150 complaints, and a weighted total at least one-and-a-half times the model's typical (median) year. A year has to stand out from its own siblings — not just sit near the worst year of a model where every year looks similar.
• Below average — index 35 or higher without clearing the full avoid bar.
• Typical — the middle of the pack.
• Better year — index 20 or under with at least four years on the road.
• Too early to call / early warning signs — years less than three years old; complaints build over a vehicle's first decade, so young years score gently unless they're already loud.
• Few reports — under 30 complaints; not enough signal for a fair score.

Mileage figures

Many owners include an odometer reading in their report. Where at least 30 reports for a year (or 8 for a specific component) include one, the pages show the median and the middle half of those readings. That's "the mileage where owners report trouble," not a lab figure.

Owner quotes

The quoted report under each component is picked because its wording matches what the largest share of sibling reports describe — the recurring failure, not the strangest story. Quotes are shown as filed, lightly cleaned for capitalization only.

What this data can't tell you

• Complaints are unverified owner accounts. People file them when they're angry, and news coverage or a recall notice can trigger waves of filings.
• Complaint volume is not a failure rate — see the denominator problem above.
• Repair costs aren't in NHTSA's file, so you won't see them here. Sites that show them are using their own submissions, not the federal record.
• A quiet year is a good sign, not a guarantee. Any used car needs its own inspection and a VIN check at nhtsa.gov/recalls.