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Title: Impact of Fuel Contents on Tribological Performance of PAO Base Oil and ZDDP

Fuel and water contents are inevitable in automotive engine oils. This study intends to investigate the impact of the addition of gasoline (3–20%) and water (1%) on the lubricating performance of synthetic base oil (PAO), with or without an anti-wear additive (ZDDP), for a steel-cast iron contact. Fuel-added PAO showed an increase in the load carrying capacity. Oil electrical conductivity and total acid number (TAN) measurements showed slightly increased conductivity and marginally increased acidity at a higher fuel concentration. In contrast, an increased wear rate, proportional to the fuel concentration, was observed in a prolonged test with constant-loading. Results suggested that the fuel addition is a double-edged sword: reducing the scuffing risk by providing stronger surface adsorption and increasing the sliding wear rate by bringing down the oil viscosity. The PAO-water blend formed an emulsion and resulted in a significantly increased load-carrying capacity, again likely due to the higher polarity and possibly acidity. For the ZDDP-containing PAO, the addition of 1% water and 3% fuel generated 24% and 52% higher wear. The phosphate polymerization level was reduced on the worn surfaces by the introduction of water but the thickness of ZDDP tribofilm was not significantly affected.
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [1] ; ORCiD logo [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Chinese Academy of Sciences (CAS), Lanzhou (China). State Key Lab. of Solid Lubrication. Lanzhou Inst. of Chemical Physics
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Energy and Transportation Science Division
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Lubricants
Additional Journal Information:
Journal Volume: 6; Journal Issue: 3; Journal ID: ISSN 2075-4442
Publisher:
MDPI
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; oil dilution; water; fuel; TAN; conductivity; scuffing; ZDDP
OSTI Identifier:
1474717

Zhou, Yan, Li, Weimin, Stump, Benjamin, Connatser, Raynella, Lazarevic, Sladjan, and Qu, Jun. Impact of Fuel Contents on Tribological Performance of PAO Base Oil and ZDDP. United States: N. p., Web. doi:10.3390/lubricants6030079.
Zhou, Yan, Li, Weimin, Stump, Benjamin, Connatser, Raynella, Lazarevic, Sladjan, & Qu, Jun. Impact of Fuel Contents on Tribological Performance of PAO Base Oil and ZDDP. United States. doi:10.3390/lubricants6030079.
Zhou, Yan, Li, Weimin, Stump, Benjamin, Connatser, Raynella, Lazarevic, Sladjan, and Qu, Jun. 2018. "Impact of Fuel Contents on Tribological Performance of PAO Base Oil and ZDDP". United States. doi:10.3390/lubricants6030079. https://www.osti.gov/servlets/purl/1474717.
@article{osti_1474717,
title = {Impact of Fuel Contents on Tribological Performance of PAO Base Oil and ZDDP},
author = {Zhou, Yan and Li, Weimin and Stump, Benjamin and Connatser, Raynella and Lazarevic, Sladjan and Qu, Jun},
abstractNote = {Fuel and water contents are inevitable in automotive engine oils. This study intends to investigate the impact of the addition of gasoline (3–20%) and water (1%) on the lubricating performance of synthetic base oil (PAO), with or without an anti-wear additive (ZDDP), for a steel-cast iron contact. Fuel-added PAO showed an increase in the load carrying capacity. Oil electrical conductivity and total acid number (TAN) measurements showed slightly increased conductivity and marginally increased acidity at a higher fuel concentration. In contrast, an increased wear rate, proportional to the fuel concentration, was observed in a prolonged test with constant-loading. Results suggested that the fuel addition is a double-edged sword: reducing the scuffing risk by providing stronger surface adsorption and increasing the sliding wear rate by bringing down the oil viscosity. The PAO-water blend formed an emulsion and resulted in a significantly increased load-carrying capacity, again likely due to the higher polarity and possibly acidity. For the ZDDP-containing PAO, the addition of 1% water and 3% fuel generated 24% and 52% higher wear. The phosphate polymerization level was reduced on the worn surfaces by the introduction of water but the thickness of ZDDP tribofilm was not significantly affected.},
doi = {10.3390/lubricants6030079},
journal = {Lubricants},
number = 3,
volume = 6,
place = {United States},
year = {2018},
month = {9}
}

Works referenced in this record:

Comparison of an oil-miscible ionic liquid and ZDDP as a lubricant anti-wear additive
journal, March 2014