How we calculate

Last updated October 2026

Every number on Throttlebook comes from code you could check by hand — never from an AI guess. Here's what goes in.

Vehicle data

Specs: NHTSA vPIC VIN decoder.
Recalls, owner complaints, crash-test stars: NHTSA. Recalls are matched by model year, so they “may apply” — confirm by VIN at nhtsa.gov/recalls.
Fuel economy: EPA fueleconomy.gov.

5-year cost to own

Depreciation, insurance, fuel or charging, maintenance, repairs, loan interest and taxes/fees. Curves are calibrated against Kelley Blue Book's 2026 5-Year Cost to Own figures and AAA's 2025 Your Driving Costs study: our estimates reproduce those 13 published figures within about 5% on average (worst case 13%). That is how well the model fits the examples it was tuned on, not a promise about your car: individual parts such as fuel and repairs can be off by much more, and used vehicles and motorcycles are less tested. Defaults: national-average insurance ($2,400/yr for a car), $3.35/gal gas, 6.35% APR for new and 11.19% for used (Experian, Q2 2026), 6% sales tax. You can change all of them.

We lean slightly high on purpose. Underestimating what a car costs is the expensive mistake.

Fair price

We start from the same depreciation curves as the cost model, which assume typical miles for the age (about 12,000 a year for cars, 4,000 for motorcycles). Each 1,000 miles over or under moves the fair price about 0.4% (1% for motorcycles), capped at +15% / −30%. The band is ±8% for vehicles up to 5 years old, ±10% to 10 years and ±12% beyond, because condition matters more with age. Below the band isn't automatically a deal: check the VIN history and get an inspection.

Affordability

We compare all-in monthly cost (payment, insurance, fuel, upkeep) with your gross income. Fits ≤ 10% (the 20/4/10 guideline), Stretch ≤ 15%, Not yet above that — with a wait-and-save plan instead of a loan offer.

Ownership Score (beta)

0–100: reliability 40 (NHTSA complaints and recalls), cost to own 35 (vs. a class benchmark), safety 25 (NHTSA stars). Same formula for every vehicle; no one can pay to change it.

Everything here is an educational estimate, not financial or mechanical advice.