Open Access

ARTICLE

Comparative Effects of CD and CF Grade Lubricating Oils on Friction Reduction and Energy-Saving Potential of Marine Diesel Engines

Yichao Zhu¹, Yixi Shao^2,3, Feng Zhu^2,3, Yi Li¹, Liangyan Zheng¹, Weiwei Wang^1,*, Leyang Dai^1,*
1 School of Marine Engineering, Jimei University, Xiamen, China
2 National Key Laboratory of Marine Engine Science and Technology, Shanghai, China
3 Shanghai Marine Diesel Engine Research Institute, Shanghai, China
* Corresponding Author: Weiwei Wang. Email: ; Leyang Dai. Email:

Energy Engineering https://doi.org/10.32604/ee.2026.086332

Received 28 May 2026; Accepted 16 July 2026; Published online 12 August 2026

Abstract

Reducing frictional mechanical losses is an important route for improving marine diesel engine efficiency and lowering energy consumption. Among the major friction pairs in diesel engines, the cylinder liner-piston ring system is directly affected by lubricant grade, lubricant aging, oxidation stability, and the ability of additives to form protective tribofilms. In this study, two commonly used marine diesel engine lubricants, CD and CF grade oils, were comparatively evaluated under simulated cylinder liner-piston ring contact conditions. A reciprocating friction and wear test was carried out at 200°C, 10 MPa, 8 mm stroke, and 5 Hz for aging durations from 0.25 h to 15 h. Friction coefficient, lubricant viscosity, oil elemental composition, Fourier transform infrared spectra, worn surface morphology, and surface elemental composition were systematically analyzed to reveal the relationship between lubricant grade, friction reduction, and energy-saving potential. The results show that CF oil exhibits lower friction than CD oil, especially after long-term high-temperature aging. After 10 h, the friction coefficient of CD oil rises rapidly to 0.21, while that of CF oil remains relatively stable around 0.175, corresponding to an approximately 16.7% lower friction coefficient for CF oil under identical test conditions. This indicates that CF oil has stronger capacity to suppress frictional energy loss. The superior performance of CF oil is attributed to its high oxidation resistance, stable viscosity evolution, high additive reserve, and the formation of S-, P-, and Zn-containing composite tribofilms on the worn surface. These findings indicate that CF grade lubricating oil has stronger friction-reduction and energy-saving potential for marine diesel engines than CD grade oil under severe thermal-frictional conditions.

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Keywords

Marine diesel engine; lubricating oil grade; friction reduction; energy consumption; cylinder liner-piston ring

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