Composition
Correct urea-water balance is central to dosing performance.
- Urea concentration
- Density
- Refractive index
Technical pillar
AdBlue / DEF / AUS 32 Analysis
Composition, contamination, storage and SCR-system diagnostic guidance.
Reviewed Jul 2026 · Oil Testing Atlas editorial teamOrientation
From a fluid result to an equipment decision.
Composition, contamination, storage and SCR-system diagnostic guidance. This pillar connects fluids, equipment, tests, abnormal findings and corrective actions.
Interpretation should distinguish specification testing, condition monitoring, troubleshooting and research analysis. The same method may support all four, but the sampling design, decision rule and strength of conclusion are different.
Reviewed Jul 2026 · Oil Testing Atlas editorial teamDiagnostic dimensions
Read the evidence as a connected system.
A result gains meaning when companion evidence predicts the same mechanism and the operating context is comparable.
Contamination
Ions, metals and hydrocarbons can damage dosing or catalyst systems.
- Metals
- Insolubles
- Hydrocarbons
SCR symptoms
Quality results must be correlated with dosing-system evidence.
- Warning light
- Deposits
- Injector blockage
Knowledge map
What to examine.
Use topics as investigation branches rather than isolated checkboxes.
01Urea concentration
Review the relevant fluid, equipment, test and abnormal-pattern evidence before selecting action.
02Refractive index
Review the relevant fluid, equipment, test and abnormal-pattern evidence before selecting action.
03Metals
Review the relevant fluid, equipment, test and abnormal-pattern evidence before selecting action.
04Storage
Review the relevant fluid, equipment, test and abnormal-pattern evidence before selecting action.
05Crystallisation
Review the relevant fluid, equipment, test and abnormal-pattern evidence before selecting action.
Sampling and data quality
A representative sample is part of the measurement.
Poor sampling can make precise analysis misleading. Fix the location, operating state, flushing practice and supporting records before comparing trends.
Open sampling guide| Control | Recommended practice | Risk if uncontrolled |
|---|---|---|
| Control 1 | Use dedicated compatible containers | Bias, contamination or a non-comparable trend |
| Control 2 | Prevent contact with copper and unsuitable alloys | Bias, contamination or a non-comparable trend |
| Control 3 | Verify current ISO 22241 requirements | Bias, contamination or a non-comparable trend |
Interpretation framework
Context before alarm.
| Question | Evidence required | Why it changes the conclusion |
|---|---|---|
| Is the sample comparable? | Location, interval, operating state and container | Sampling variation can mimic a condition change |
| Did the fluid system change? | Grade, make-up, filtration and maintenance | Dilution and discontinuities alter concentration |
| Is the signal corroborated? | Companion tests, inspection, filters and machine data | Independent agreement increases confidence |
| Which rule governs action? | OEM, product specification, contract and jurisdiction | Universal limits are rarely defensible |
Related tests
Browse all tests →Build a panel around the decision.
test
Kinematic Viscosity
Confirm grade and detect dilution, oxidation, shear or contamination. Learn the method principle, sample controls, interpretation limits and related diagnostic evidence.
- tests
- physical properties
test
Viscosity Index
Describe the temperature sensitivity of lubricant viscosity. Learn the method principle, sample controls, interpretation limits and related diagnostic evidence.
- tests
- physical properties
test
Elemental Analysis by ICP-OES
Screen wear metals, contaminants and additive elements. Learn the method principle, sample controls, interpretation limits and related diagnostic evidence.
- tests
- wear and elemental analysis
test
PQ Index
Detect the relative amount of ferromagnetic debris, including particles too large for ICP response. Learn the method principle, sample controls, interpretation limits and related diagnostic evidence.
- tests
- wear and elemental analysis
test
Analytical Ferrography
Examine wear-particle morphology when routine trends suggest abnormal distress. Learn the method principle, sample controls, interpretation limits and related diagnostic evidence.
- tests
- wear and elemental analysis
test
Particle Count
Quantify fluid cleanliness and support contamination-control decisions. Learn the method principle, sample controls, interpretation limits and related diagnostic evidence.
- tests
- contamination
test
Karl Fischer Water
Quantify dissolved, emulsified and finely dispersed water. Learn the method principle, sample controls, interpretation limits and related diagnostic evidence.
- tests
- contamination
test
Acid Number
Trend acidic constituents associated with oxidation, contamination or additive chemistry. Learn the method principle, sample controls, interpretation limits and related diagnostic evidence.
- tests
- chemical condition
The Oil Testing Atlas provides general educational information and does not replace laboratory review, engineering judgement, equipment inspection, OEM instructions or safety procedures.