# Auxiliary Engine

> Auxiliary Engine means a non-propulsion engine primarily providing power, installed or intended for installation in non-road mobile machinery

**Term:** Auxiliary Engine  
**Last updated:** 2026-07-29

## Definition

## What Auxiliary Engine Means in a Contract

An Auxiliary Engine, as used in a contract, is a power source that does not move a machine forward but instead runs other functions, such as generators, pumps, hydraulic systems, or refrigeration units mounted on non-road mobile machinery. Contracts that manufacture, supply, lease, or maintain such machinery use this definition to separate obligations relating to propulsion systems from those relating to secondary power units, because the two are often subject to different technical standards and different commercial terms.

The term matters because equipment sold to sectors such as [construction](https://www.genieai.co/industry/construction) and [mining](https://www.genieai.co/industry/mining) frequently includes both a main propulsion engine and one or more auxiliary engines. A supply or maintenance agreement that fails to distinguish between the two risks ambiguity over which warranty terms, service intervals, or emissions certifications apply to which engine.

Because the definition hinges on function rather than size or fuel type, an Auxiliary Engine can be a small generator set or a substantial power unit, provided its role is to supply power rather than to move the vehicle or machine. This functional test is what courts and technical regulators typically apply when interpreting such clauses.

## How Auxiliary Engine Is Defined or Measured

Most contracts adopt a definition close to the one used here: a non-propulsion engine, primarily providing power, installed or intended for installation in non-road mobile machinery. Precision in each element of this phrase matters.

## Context

### Relevant circumstances

- Purchasing or leasing heavy machinery for construction or industrial sites.
- Forming joint ventures to undertake large-scale projects requiring specialized machinery.

### Relevant sectors

- Construction
- Mining

## Relevant contract types

- [Construction Agreement](https://www.genieai.co/en-us/template-type/construction-agreement)
- [Manufacturing Agreement](https://www.genieai.co/en-us/template-type/manufacturing-agreement)
- [Construction Phase Plan](https://www.genieai.co/en-us/template-type/construction-phase-plan)

---

This is the Markdown representation of [https://www.genieai.co/en-us/define/auxiliary-engine](https://www.genieai.co/en-us/define/auxiliary-engine), provided for AI agents and crawlers. The HTML page is canonical. See [/llms.txt](https://www.genieai.co/llms.txt) for the full content map.