## 1 Introduction  
In metal-mechanic processes, using the appropriate type of fluids and lubricants, together with the proper working materials, could reduce the friction and wear of machinery and tooling components. This also increases machine efficiency in terms of workpiece surface finish and tolerances, thus improving machines' operative life and eventually reducing the vibrations and required cutting force [1; 2; 3; 4; 5]. According to Oakridge National Laboratory (USA), wear and friction contribute to about 25% of worldwide total energy loss [6]. Approximately 85% of lubricants used worldwide are petroleum based [7]. The ecological issues related to the extensive usage of these oils and the geopolitical strategies regarding crude oil exploitation are the main drivers for the development of novel alternatives from eco-friendly raw materials [8; 9; 10]. To prevent adverse effects on industrial operators and the environment, intensive research concerning improved cooling and lubrication performance is recommended. Fluids and lubricants have an impact on heat dissipation and metal-mechanic process parameters such as cutting speed, feed rate, and depth of cut [11]; they also provide a proper working component interface, i.e., help in washing away chips and debris from machined surfaces. Natural lubricants, such as soybean, sunflower, and corn oils, act as antifriction components, which facilitate these manufacturing processes while reducing the risks associated with machinery damage or failures. According to [PERSON] et al. [10], \"green\" processing should be one of the most common methods applied to obtain the optimum output of machine components. During machining, the coolant and lubricant performance must be favorable to improve quality and productivity. Elevated temperatures, high pressures, and other processing factors cause a more rapid deterioration of fluids and lubricants, leading to problems caused by their frequent replacement, and thus, increasing industrial production costs. Furthermore, the usage of these materials has various disadvantages, such as environmental impact, increased material costs, and health hazards, i.e., respiratory and skin diseases due to their toxic or nonbiodegradable characteristics [10; 12; 13; 14; 15; 16]. Recently, vegetable fluids are getting more attention as novel potential alternatives to petroleum-based lubricants or coolants due to their inherent properties and performance, such as being renewable, biodegradable, and nontoxic. It has been observed that vegetable fluids minimize carbon monoxide emission levels, which is one of the main reasons for their increased application in the industrial field. Vegetable fluids possess excellent biodegradability with excellent applicability to tribological problems. Although natural or vegetable fluids have excellent properties and applicability, they also have certain drawbacks that affect their performance. However, vegetable fluids have shown limited industrial applicability due to their low temperature performance [17; 18; 19], poor thermal or oxidation stability [19; 20; 21; 22; 23; 24; 25], and the occurrence of other tribochemical degrading processes [26; 27; 28] under specific working conditions of pressure, stress, temperature, and environment. A critical problem with vegetable fluids is their limited oxidative stability, which adversely impacts their shelf life and performance [29; 30; 31]. For instance, a low oxidative stability results in a faster oxidizing rate; consequently, the fluid polymerizes and becomes thick [32]. The oxidative instability of vegetable lubricants is attributed to the structural \"double bond\" in the fatty acid part of the \(\beta\)-CH group of the alcoholic (glycerin) components [31]. Furthermore, vegetable fluids chemically interact with metallic working surfaces at high temperatures, forming a high strength fluid film or layer, resulting in reduced friction and wear. These strong intermolecular interactions are resistant to temperature alterations, which results in high viscosity [33].