Vehicle data and calculator methodology

Service specifications

We compile oil, fluid, tire, torque and maintenance facts from manufacturer owner manuals, service information and towing guides. A blank source is not permission to estimate. We show "Not published" instead.

A year-specific sheet needs at least six populated fields. If adjacent years carry the same data and do not add a distinct decision, we keep the comparison on the model page instead of publishing another URL.

Vehicle catalog and fuel economy

U.S. EPA FuelEconomy.gov supplies engine choices, MPG, fuel type, emissions and annual fuel cost. NHTSA supplies recall campaigns, 5-Star safety ratings and the free vPIC VIN decoder. Builds read committed JSON and never call those catalog, recall or safety services at request time.

Energy prices

Calculator defaults use the public U.S. Energy Information Administration historical gasoline and residential electricity tables. The refresh script reads the public tables without an API key, records the source date, and commits the result before a build. Rates are planning inputs, not a local utility tariff.

VIN decoding

The recall tool does not decode a VIN on first load. After a visitor chooses Decode VIN, the browser sends that VIN directly to NHTSA vPIC and displays the returned fields. Zam Green does not store the VIN or put it in the page URL.

Calculator formulas

Gas cost equals miles divided by MPG, multiplied by dollars per gallon. EV energy cost equals miles divided by miles per kWh, multiplied by dollars per kWh. Tire diameter equals wheel diameter plus twice the sidewall height.

Corrections

Send the vehicle year, engine, disputed field and a manufacturer-document link through the correction request page. We review the cited record and date the correction.