Source: https://guthlabs.ai/docs/instruments/fuel-economy-calculator/implementation/

instrument implementation / implementation-contract

# Fuel Economy Calculator implementation

A source-bound implementation contract for Fuel Economy Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t4-091

**Effect**: Computation or source lookup only

## Input and validation requirements

The formulas have no input validation for zero denominators or physically invalid fill-up data. Zero fuel makes MPG undefined (or Infinity in plain JavaScript), and zero distance makes L/100km undefined.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "miles_driven": 360,
    "gallons_used": 12,
    "gallon_type": "US"
  },
  "expected_outputs": {
    "MPG": 30
  },
  "working": "1. miles_driven = 360 mi.\n2. gallons_used = 12 US gal.\n3. MPG = miles_driven ÷ gallons_used.\n4. MPG = 360 ÷ 12 = 30 MPG."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/fuel-economy-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/fuel-economy-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/fuel-economy-calculator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche4/tranche4-results.json`