DOES THE MS TEST PREDICT FIELD PERFORMANCE? 600116
The major automobile makers have jointly developed a series of laboratory engine-test procedures for appraising motor oils blended for API Service Classification MS. How well the new test predicts field performance has not been satisfactorily answered.
Twelve oils run in 40 vehicles for a total of over 2 million miles have been evaluated in the MS Test. Because different engines in the same field test responded differently to identical oils, the laboratory test could not be expected to correlate with all field results. However, the ranking of oils in each field test was correctly predicted for at least one make of engine as regards over-all sludge, ring plugging, screen clogging, ring sticking, and rust. Piston varnish and wear were incorrectly predicted.
Duplications occur in the MS procedure and should be eliminated. For predicting the results for our two field tests, MS Sequences I and IV tell the same story for wear; MS III and V tell the same story for engine cleanliness. The MS Test satisfactorily supplants several engine tests long used in motor-oil development work, but it is not broad enough to cover all aspects of such development.