Quantitive method for determining the aging influence on an engine oil

There sit of great interest to determine effects of aging on an engine oil quantitatively. The inventive method provides for detecting two variables of the engine oil, wherein the one of the two variables is the viscosity and the other size of the acid content of the engine oil. Thereafter, a first variation Ax of the detected first variable is determined to a default value and the second size based on the difference Ax, estimated. By determining a second deviation of the estimated second variable Δν ν As various aging effects have different effects on the two sizes, individual aging effects can be determined quantitatively targeted.