Savant, Inc. - Technical Papers

Work was initiated because of concerns that ring belt and piston undercrown temperatures of 250°C and higher in modern high performance engines may cause a significant increase in carbonaceous deposits in these areas. In the absence of an engine test and reference oils for such ring-belt deposit evaluation, the TU3MH piston varnish rating test and its four associated reference oils as well as a Matrix of GF-2 and potential GF-3 engine oils were chosen to study correlation.

Two groups of TU3MH engine stands were used to generate data through 1998, one group in Europe and one group in North America. The former, using special pistons, showed fair correlation between the TU3MH and TEOST MHT-4 protocol (R² = 0.73) while the latter, using dealer-supplied pistons was somewhat poorer (R²=0.55). Analysis of the combined data plus further tests in 1999 using special pistons showed that the total data could be separated into two discrete groups both showing high correlation of varnish with carbonaceous deposits. Similar slopes of the two groups of data suggested a consistent relationship between the varnish and carbonaceous deposits but displaced in varnish severity by some third factor. Further analysis indicated that the third factor was associated with choice of special or common pistons. Importantly, it was indicated that significant carbonaceous ring-belt deposits may still form even when piston varnish levels are very low.

"Engine Oil Deposits and the TEOST -- Protocol 33 and Beyond"
    Written by T.W. Selby and Jennifer Richardson, Savant, Inc. and Dennis Florkowski, Chrysler Corp.,
    - SAE Paper #962039, SAE International Fall Fuels and Lubricants Meeting and Exposition in San Antonio, Texas on October,
      14-17, 1996.

Abstract

In its first use in simulating engine operating conditions, the Thermo-oxidation Engine Oil Simulation Test (TEOST®) was applied to the study and deposition measurements of engine oils under turbocharger operating conditions in a technique called Protocol 33C. Building on a previous paper, the authors present data and discussion on the factors involved in the high temperature cyclic test conditions of the TEOST and reemphasize differences between it and steady-state oxidation tests.

Some new studies are discussed which involve application of the TEOST apparatus at lower temperatures using simulated crankcase gases. These are believed more reflective of piston deposit conditions. Preliminary studies indicate that results from this new lower-temperature protocol correspond to known reference engine oils in regard to piston deposits and other measured factors.

"The Development of a Thermo-Oxidation Engine Oil Simulation Test (TEOST)"
    Written by D.W. Florkowski, Chrysler Corporation and T.W. Selby, Savant, Inc.
    - SAE Paper #932837, presented by D.W. Florkowski at SAE International Fuels and Lubricants Meeting and Exposition in
       Philadelphia, Pennsylvania on October 18-21, 1993.

Abstract

This paper concerns a bench test developed to simulate the effect of engine operating conditions on the oxidation and deposit-forming tendencies of engine oils. The so-called Thermo-oxidation Engine Oil Simulation Test (TEOST) is carried out under temperatures and other environmental conditions identified as being significant in the internal combustion engine. These parameters can be readily modified to reflect different aspects of deposit conditions and/or different forms of the mechanical design of reciprocating engines.

The most important aspect of the TEOST is the separation of the oxidation process into the two aspects believed to be present in the engine, (1) the preparation of oxidation precursors in the so-called 'Reactor' representing the engine sump and other moderately heated areas of oil exposure, and (2) the 'Depositor' representing those areas of the engine where temperatures are such that the completion of the deposit-forming oxidation mechanism can be induced. Many variations of time, temperature, oil flow rate, cycling rate of oil temperature, and conditions of oxidation precursor formation were investigated. These ultimately let to a test protocol showing particular promise regarding the evaluation of modern engine oils.