Development and Performance Aspects of Jojoba Based Lubricant Formulations for Two Stroke Gasoline Engines 932795

Two-stroke engines are gaining importance as they provide smaller, simple machines having less moving parts than four stroke engines. In India the majority of them employ mixed lubrication systems. Lubrication requirements of two-stroke, air cooled engines are different than that of a four-stroke engines and need some specific characteristics in the oil formulation. Due to enviromental and lubricant conservation considerations, carburetors will run leaner and lower oil consumption is expected in the future. This situation may result in higher piston temperatures leading to increased tendency of ring sticking and piston seizure. With a view to conserve and eventually replace petroleum base stocks, alternate and renewable sources of lubricating oil are being considered. The vegetable oils, in general, provide good shear stability, miscibility with mineral oil and gasoline fuel, and easy biodegradability. The oil derived from jojoba appears to be a posible substitute of mineral base stocks. The lubricant formulations using jojoba oil as a base stock have been evaluated through physico-chemical tests and bench studies using two-stroke engines. The jojoba oils modified with additives have indicated that a superior quality lubricant can be developed. The jojoba-based oils were developed for engines requiring a fuel-oil premix. A lubricant formulation based on jojoba oil, when evaluated through an engine test, provides clean piston skirt, clean piston undercrown, rings free from deposits (sticking) and negligible exhaust port blocking. The performance of this jojoba oil formulation is comparable to that of a commercial mineral based oil of API TC quality presently used in India. It is, therefore, concluded that jojoba oil formulations are capable of working successfully in two stroke gasoline engine applications.

Increasing demand of crude oil, depletion of hydrocarbon sources and unsuitability of indigenous crudes for the production of high quality lubricating oil base stocks have necessiated initiation of steps to conserve and find suitable substitutes. Jojoba oil is a renewable resource which can be considered as an attractive alternate because there is ample scope for its cultivation in India [1].

Jojoba, which was originally a wild shrub growing in the southwest American desert, is now cultivated as a commercial crop worldwide. At present over 50,000 hectares are under cultivation and the seeds industry alone is worth over $700 million annually. Interestingly, research work on jojoba began in India as far back as 1965 when its potential to green the deserts of Rajasthan state was being explored. Now the land under jojoba cultivation in India will increase to over 50,000 hectrares by 2000 AD. The seeds of jojoba contain about 50% of an oil which differs from other vegetable oils in chemical composition. It is a non-glyceride oil which is structurally very similar to industrially important sperm oil. It is composed of a mixture of monoesters of straight chain acids and alcohols. The esters have chain lengths in the range of C34-C50 (even numbered) in which C40 and C42 esters are predominant. The acids and alcohols that make up jojoba esters are monounsaturated. The active functionalities of double bond and ester group give places for chemical reactions. A number of commercially important products can be formulated which are finding applications in cosmetics, lubricants, pharmaceuticals, etc.[2].

Realising the potential of jojoba oil, it has been investigated for various industrial and engine lubricant applications. For such applicantions, it has been used both in its raw and modified form both as a base stock or blending component [3-8] and as an additive (singly or in combination with other additives) [8-13]. Jojoba oil has promising lubricant characteristics. In the present work, its suitability as a base stock for lubricant used in two- stroke-cycle engines (which use mixed lubrication system) was studied. The studies included laboratory analysis, modification of needed properties by convential additives, and finally performance studies in an bench engine test.