Some basic rules should be observed during a changeover according to the following test scheme. This can reduce any problems caused by incompatible oils.
1st Level: First, it is checked whether the products to be mixed have been produced with similar base oils. If this is the case, viscosity and additives must still be checked If the base oil types are different, re-oiling guidelines must be followed to ensure that the tramp oil content remaining in the system is less than 2%.
Please note: Mixing of oils with different base oils should be avoided if possible.
2nd Level: If the oils match in terms of the base oil type, a comparison of the viscosities, e.g. at 40 °C, is appropriate. It is one of the most important oil properties and is largely responsible for the formation of the lubricating film.
However, for oils with different viscosities, the viscosity does not change linearly with the ratio of the blend components. The viscosity expected from mixing must be calculated with a special program (Viscosity Manager, MobilCalc). After that, it must be decided whether the viscosity to be expected from the mixture can be tolerated.
3rd Level: The most difficult part is the comparison of additive packages. Specialized knowledge about the exact structure of the formulation is often necessary here. A comparison of the data provided by the oil manufacturer in safety data sheets or product information is usually not sufficient for this purpose. In addition to the analysis of the two comparative products with the question "compatibility test", you will receive a laboratory report from the experienced OELCHECK tribologist, in which the additives are quantified and a possible incompatibility is commented.
There are also some generally applicable references, e.g. in product information, which can be used for an initial estimate:
- Are markings according to DIN or ASTM standards comparable, are the same requirement standards (HLP, CLP, TD-L, SAE, API, ACEA) fulfilled?
- Do the oils meet the same general specifications, are they approved by the same equipment manufacturers?
- Are the same mechanical test procedures (FZG test, four ball test, Brugger, FE8, foam test) met?
- Are characteristic values such as viscosity, viscosity index, density, ash content or flash point comparable?
Do not mix the following oils:
- Zinc-free and zinc-containing hydraulic and circulating oils
- Oils with detergent and non-detergent properties
- Glycol-based synthetic oils with all other synthetic oils
For a detailed compatibility assessment, the oil manufacturer's technical service is usually available for (hopefully written) information.