Sulphate ash

OELCHECK test instrument: Phoenix Microwave Furnace
Sample quantity: 3 ml
Unit: % (weight)
Test result: sulphate ash
Analysis for: engine oils and greases
Brief description:

The sulphate ash is determined by heating the sample to temperatures of 775 °C. At this temperature all organic elements in the sample "combust". All that remains are ashes, which consist of metallic oxides and impurities.

By smoking this with concentrated sulphuric acid, the oxides in the ashes are transformed into sulphates. The difference in weight of the remains is then determined.


The sulphate ash content of new and used lubricants changes as a result of factors such as metal abrasion or solid impurities (dust).

The ash content of engine oils enables conclusions to be drawn on potential oil additive deposit formation on hot engine parts. This is why the permissible ash content is listed in specifications.

Sulphate ash in lubricating greases consists of metallic soaps, inorganic thickening agents and other additives. They are altered by abrasion and impurities and allow conclusions to be drawn on matters such as bearing wear in comparison with new grease.

Underlying test standard: DIN 51575, OPM 028
Deviating methods: ASTM D874