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Previous research to understand the mechanism for piston deposit formation in the Sequence IIIG engine test has focused on characterizing the piston deposits. These studies concluded that, in addition to lubricant derived materials, Sequence IIIG piston deposits contain a significant amount of fuel-derived carbonaceous material. The presence of fuel degradation by-products in Sequence IIIG deposits shows that blow-by is a significant contributor to deposit formation. However, blow-by can either assist in the degradation of the lubricant or can simply be a source for organic material which can be incorporated into the deposits. Therefore, a series of modified Sequence IIIG engine tests were conducted to better determine the effect of blow-by on deposit formation. In these studies deposit formation on different parts of the piston assembly were examined since different parts of the piston assembly are exposed to different amounts of blow-by.

The CEC-L-78-T-99 test, also known as the VW PV 1452 procedure, is a severe test of a lubricant's ability to prevent piston deposits and ring stick in a passenger car diesel engine. The test features in the ACEA “B” sequences and also, at a somewhat higher performance level, in various proprietary specifications. The demanding nature of the test means that it exerts a major influence upon the formulation of lubricants meeting these performance standards. Passing this test with the SAE 5W-30 or 0W-30 grade oils needed for fuel economy can be a difficult task and obtaining satisfactory results from statistically designed experimentation can be plagued by instances of ring stick. A modified test procedure has been developed with the intention of avoiding the loss of data due to ring sticking. By stopping the test at intervals during the procedure, intermediate piston ratings can be obtained, this does not affect the outcome of the test.