Engine Oil Fuel Dilution Tracking for Accurate Oil Change Intervals

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Solution Overview

Problem

Existing methods fail to accurately account for changes in lubricant mass due to fuel input and output during internal combustion engine operation, leading to inaccurate lubrication properties and potential engine damage.

Innovation Solution

A method and control unit for continuously determining fuel differential mass in the engine oil, using operating mode-specific models and parameters to calculate a standardized fuel equivalent, which improves the determination of oil change intervals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If fuel dilution of engine oil is allowed to occur during operation, then the lubrication system can handle fuel contamination, but the viscosity of the engine oil reduces and lubrication film thickness decreases

Engineering Contradiction:
Improvetolerance to fuel contaminationVSAvoidlubrication quality
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

The patent implements a feedback mechanism by continuously monitoring engine operating parameters (fuel injection quantity, engine speed, load, temperature) and using this information to dynamically calculate and update the fuel mass in the lubricant. This real-time feedback allows the system to track lubricant quality changes and predict when oil change is necessary, resolving the contradiction between fuel tolerance and lubrication reliability.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The system performs self-assessment by using the engine's own operating data to determine fuel dilution levels and lubricant condition. The control unit calculates the fuel mass in the lubricant based on measured operating parameters without requiring external intervention or additional sensors, enabling the lubrication system to self-monitor and self-manage its quality.

Inventive Principle:
Principle #25Self-service

2Quantity of substance

If fuel evaporates from the engine oil in the intake manifold, then the air-fuel mixture can be enriched, but this causes undesirable combustion conditions and potential engine damage

Engineering Contradiction:
Improvefuel recovery from lubricantVSAvoidair-fuel mixture enrichment
Core Design Contradiction:
Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The system takes preliminary action by calculating and predicting the fuel mass in the lubricant before significant evaporation occurs. By continuously monitoring operating parameters and tracking fuel dilution trends, the system can predict when fuel evaporation might cause harmful enrichment, allowing preventive measures to be taken before damage occurs.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The control unit acts as an intermediary by processing operating parameter data and translating it into meaningful fuel mass calculations. This intermediary function allows the system to indirectly measure fuel content in the lubricant through operating parameters, enabling monitoring of fuel evaporation risks without directly measuring evaporated fuel.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Ease of operation

If the fuel mass in the lubricant is not accurately determined, then the lubrication system operates without precise monitoring, but oil change intervals cannot be accurately predicted

Engineering Contradiction:
Improveoperational simplicityVSAvoidfuel mass determination accuracy
Core Design Contradiction:
Ease of operationVSMeasurement precision

Solution Approach 1:

The patent replaces complex physical measurement systems with a calculation-based approach. Instead of using sensors to directly measure fuel mass in the lubricant, the system substitutes mechanical/physical measurement with a computational model that calculates fuel mass based on operating parameters (fuel injection quantity, engine speed, load, temperature), achieving precise determination through mathematical relationships rather than direct measurement.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The control unit performs multiple functions using the same set of operating parameter measurements. The same input data (fuel injection quantity, engine speed, load, temperature) used for engine control is also utilized to calculate fuel mass in the lubricant, determining oil change intervals, and monitoring lubrication quality, creating a universal system that maximizes the utility of available data.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables reliable assessment of fuel mass in the lubricant, ensuring proper lubrication and extending engine component life by accurately predicting oil change intervals.

Implementation Method 1

This can be reversed by the evaporation of the fuel when the lubricant is at operating temperature.

Methodology Applied
Scientific EffectEvaporation: Evaporation

Implementation Method 2

A method and control unit for continuously determining fuel differential mass in the engine oil, using operating mode-specific models and parameters to calculate a standardized fuel equivalent

Methodology Applied
Scientific EffectMass balance calculation:

Data Source

PatentEP3730750B1Method for balancing a fuel mass in a lubricant of a combustion chamber, combustion engine and motor vehicle
Publication Date: 2026.01.28 VOLKSWAGEN AG
  • EP3730750B1 patent drawingFigure 1
  • EP3730750B1 patent drawingFigure 2
  • EP3730750B1 patent drawingFigure 3

AI summary

The present invention relates to a method for balancing the fuel mass in a lubricant of an internal combustion engine (1) during operation of the internal combustion engine (1) by: starting an operating cycle of the internal combustion engine (1); detecting an operating mode (BM, SB; NB); determining an engine oil mass (mOil); continuously determining a fuel differential mass from a fuel input (EM) and/or a fuel output (AM) in the engine oil mass (mOil) as a function of the detected operating mode (BM, SB; NB); continuously determining a total fuel mass from a starting value of the total fuel mass and from the summed fuel differential mass; determining a normalized fuel equivalent (Än) from the total fuel mass. The invention further relates to a control unit (7) and an internal combustion engine (1) for carrying out the method according to the invention.