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 compiled service sheet needs at least six populated fields. EPA vehicle pages can exist without a compiled service sheet and will show fuel economy instead of service quantities. 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.

What a source check means

Source attribution records where a fact was compiled and when the reference was accessed. Independent page-level review also checks the exact document section, engine, market, quantity basis and procedure. Priority pages marked as awaiting source review have not completed that separate check. An access date is not a claim that the whole page was independently verified.

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.

Oil buying plans

Whole-container mode subtracts suitable oil already owned from the fill quantity, then compares 5-qt jugs and 1-qt bottles at entered prices. DIY checkout cost adds filter, labor allowance, tools and entered taxes and disposal fees. Per-quart mode values all oil used instead. Saved plans restore assumptions; they do not establish an oil approval or filter fitment.

Passenger trip settlement

Each leg adds estimated or entered fuel spending to tolls and parking, rounds the total to cents, and splits it equally between selected travelers. Extra rounding pennies go in traveler-list order. Amounts paid are compared with shares. Final transfers appear only when the total paid equals the included trip cost.

Charging memberships

Paid energy equals station energy minus complimentary energy applying equally to both plans, with a minimum of zero. Monthly net saving equals paid energy multiplied by the nonmember-to-member rate difference, minus the fee. With a positive rate discount, break-even paid kWh equals fee divided by that discount. Prices are editable examples, not live station quotes. The period assumes equal charging demand in each billed month and excludes taxes, session and idle fees.

Oil service deadlines

The entered mileage and calendar limits come from the user, not a universal service recommendation. Mileage due equals last-service mileage plus the interval. Calendar months are added with end-of-month clamping. Future mileage is projected from the reference-date odometer and expected weekly driving; the earlier deadline applies. Saved service history is a user record, not verification of performed maintenance.

PHEV public charging

Battery energy divided by charging efficiency gives wall energy. Electric-only miles equal battery energy divided by battery-side kWh per 100 miles, multiplied by 100. Per-minute cost uses wall energy divided by average accepted wall kW, multiplied by 60 minutes and the station rate. Fees are added, then compared with gasoline for the same distance. Session costs are rounded to cents before comparing. Blended gasoline use is outside this calculation.

Towing fuel budgets

Fuel gallons add towing distance divided by towing MPG to unhitched distance divided by unloaded MPG. Scenarios change only towing MPG. Tank range uses the entered usable tank minus a percentage reserve, multiplied by towing MPG. No towing MPG is inferred from trailer weight, and range is not a safe-distance guarantee.

Lease mileage decisions

Projected usage adds current odometer minus delivery odometer to entered future monthly miles times months left and extra trips. The final forecast rounds up to whole miles. Excess miles are measured against the whole-lease driven-distance allowance. A confirmed package comparison adds purchase price, fees and uncovered excess charges, then subtracts only usable unused-mile credit. Costs round to cents. Lower/higher driving scenarios change monthly miles by 20%; extra trips stay fixed. Early termination and buyout are outside the calculation.

Transmission service budgets

Confirmed drain quantity times entered cycles gives fluid used. Owned fluid is deducted once; the remainder rounds up to whole containers. Quantities use thousandths of a US quart to preserve container boundaries. The budget adds plan-wide parts, tools and fees plus labor per cycle. Shop savings appear only for a confirmed matching quote. Optional ideal mixing uses one minus the retained fraction raised to the cycle count, assuming complete mixing, identical drains and constant total capacity. It is not a measured percentage or a service recommendation.

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.