27th Annual General Meeting 18th
– 21st April 2015 Barcelona, Spain
The Development of Energy Efficient
Greases Dr Gareth Fish PhD BSc CLS CLGS
The Lubrizol Corporation, Wickliffe, Ohio, USA
Abstract Under pressure from governmental legislation, original equipment manufacturers (OEMs) have been focused on improving the efficiency of engines and drivetrains. There was little focus on improving the efficiency of other automotive components. With the desire to utilize every means of potential efficiency saving, all moving componentry on a typical automobile is now being scrutinized for friction and energy losses. This includes the greases used in the wheel and accessory equipment bearings, and transmission components, including universal joints (UJs) and constant velocity joints (CVJs), which transmit power and motion from the gearbox to the wheels.
There are two main contributors to energy losses in bearings: churning through the grease; and friction losses due to sliding of the cage against the rolling elements and raceways. By optimising the lubrication of the bearings, theoretical improvements in energy efficiency are possible, but as bearings are extremely efficient, measuring the losses is a significant challenge.
In components that have significant sliding contacts, such as plunging CVJs, lower friction greases have been developed. Initially they were developed to reduce the noise, vibration and harshness (NVH) profile of transmissions, but now more focus is being given to their application to improve energy efficiency.
Historically, friction coefficients of greases have typically been measured using an Optimol Instruments™ SRV tester. This has been standardized as DIN 51834 for friction measurements. However, published papers show that many users of the instrument do not follow the standardized conditions to determine the friction coefficients of greases. Other tests used
to measure friction include the high frequency reciprocating rig (HFRR), the Cameron Plint TE77, and the sliding 4-ball wear tester.
Today, grease frictional losses are not just an issue for the automobile industry but also for industry in general as users seek to improve energy efficiency. This paper looks at friction and efficiency losses in greases and the application of friction modifiers to potentially reduce the frictional losses in grease- lubricated componentry in a wide variety of applications.
Introduction
The last 30 years have seen an increased focus on improving the efficiency of automobiles and commercial vehicles, both from the perspective of resource conservation and greenhouse gas reduction. Government legislation has forced vehicle manufacturers to make engines and drivelines significantly more efficient than they were in the 1980s. Base oil viscosities of crankcase oils have fallen from a then typical SAE 20W-50 to the recently published SAE 0W-16 standard. The implications of the legislation, along with changes to hardware and operating conditions have improved crankcase and driveline lubricants efficiency. Since 1990, there has been a significant reduction (25%) in the amount of fuel consumed per mile by passenger cars and light trucks. This is despite the average vehicle now weighing approximately 15% more than it did then due to the incorporation of more safety features and ancillary equipment. In 2014, according to Wyrley-Birch (1) in his presentation at the 10th ICIS Pan American Base Oils & Lubricants Conference, we have entered the “Era of Efficiency.”
While the spotlight was on the energy efficiency of engines and drive trains of vehicles, there was little or no focus on other components. With the desire to capture every means of
Continued on page 14 12 LUBE MAGAZINE NO.129 OCTOBER 2015
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