Lubricant additive composition suitable for lubricating two-stroke engines fueled with heavy fuels

Abstract

A lubricant suitable for lubricating a two-stroke cycle engine which is fueled with a liquid fuel having a volatility less than that of gasoline comprises an oleaginous synthetic ester, a normally liquid solvent having a kinematic viscosity of less than about 5 or 2 mm.sup.2/s at 100 C. and a nitrogen-containing dispersant bearing a hydrocarbyl group of at least 26 carbon atoms and having a nitrogen content of at least 4 percent by weight. The nitrogen content of the lubricant is at least about 0.3 percent by weight.

Claims

1. A method for lubricating a two-stroke cycle internal combustion engine comprising the steps of: supplying to a two-stroke internal combustion engine designed to operate on only gasoline, a liquid fuel selected from the group consisting of jet fuel, diesel fuel, kerosene, and a middle distillate and a lubricating amount of the lubricant composition, the lubricating composition comprising; (a) at least about 5 percent by weight of an oleaginous synthetic ester; (b) at least about 5 percent by weight of a normally liquid solvent other than an oil of lubricating viscosity or the oleaginous synthetic ester having a kinematic viscosity of less than about 2 mm.sup.2/s at 100 C.; and (c) about 3 to about 30 percent by weight of a nitrogen-containing dispersant bearing a hydrocarbyl group of at least 26 carbon atoms and having a nitrogen content of at least 3 percent by weight; wherein the nitrogen content of the lubricant is at least about 0.2 percent by weight; and wherein the engine has a power output of at least about 150 kW (201 horsepower); resulting in said engine being able to operate on said fuel without premature engine failure due to said fuel.

2. The method of claim 1, wherein said fuel is jet fuel.

3. The method of claim 1, wherein the engine is a spark-ignited engine.

4. The method of claim 1, wherein the engine is a stratified charge engine.

5. The method of claim 1, wherein the liquid fuel is a middle distillate fuel.

6. The method of claim 1, wherein the fuel and lubricant composition are premixed externally to the engine.

7. The method of claim 6, wherein the amount of the lubricant mixed in the fuel is about 1 percent to about 6 percent by weight.

8. The method of claim 1, wherein the engine is equipped with a direct injection fuel system.

9. The method of claim 1, wherein the lubricant is not premixed with the fuel externally to the engine.

Description

EXAMPLES

(1) The invention will be further illustrated by the following examples, which set forth particularly advantageous embodiments. While the Examples are provided to illustrate the present invention, they are not intended to limit it.

Example 1

(2) A lubricant composition is prepared containing the following components:

(3) 22.9% synthetic ester oil basestock based on pentaerythritol, 12 mm.sup.2/s at 100 C.

(4) 18.5% Stoddard solvent

(5) 12.2% mineral oil, 325 Neutral

(6) 25.7% polyisobutylene, molecular weight about 1000

(7) 1.8% bright stock

(8) 8.3% succinimide dispersant, 86.5% active chemical, 13.5% diluent oil, TBN 100, nitrogen content 4.1% (4.73% excluding diluent oil), having alkyl substituent groups of about 1000 M.sub.n.

(9) 7.7% Mannich dispersant, 88% active chemical, 12% diluent oil, nitrogen content 1.13% (1.28% excluding diluent oil)

(10) 1.8% of the condensation product of isostearic acid and tetraethylenepentamine (neat; nitrogen content 6.35%)

(11) 1.0% minor components (e.g., antioxidant, corrosion inhibitor, emulsifier, friction modifier)

Example 2

(12) A lubricant formulation is prepared with the same composition as that of Example 1, except that the amount of 325 Neutral oil is decreased to 4.2% and the Stoddard solvent is replaced with 26.5% kerosene.

Example 3 (Comparative)

(13) Example 1 is duplicated but omitting the succinimide dispersant and proportionally increasing the amounts of the other components.

Example 4 (Comparative)

(14) A premium grade original equipment manufacturer's oil designed for direct fuel injected outboard engines consuming gasoline is provided. It is believed to contain 46.9% mineral oil (325 to 650 Neutral), 15% bright stock, 22% conventional solvents, and 16.1% commercial two-cycle gasoline additives.

(15) Certain of the above compositions are tested in lubrication of a 168 kW (225 hp) outboard engine (Optimax from Mercury Marine) operated with a stratified fuel charge. The engine is fueled with an aviation fuel known as AvJet A, which is a JP5-type fuel, 700 ppm sulfur, flash point 47 C. (Jet A fuel is described in the above Kirk-Othmer reference, pages 331-332, with reference to ASTM D1655.) The fuel contains the lubricant of Example 1, 2, or 3, using a fuel/lubricant ratio of 32.1. The propeller shaft is attached to a dynamometer to simulate real-world torque and load. The engine is operated under conditions of an endurance test cycle, consisting of repeated cycles of 4 minutes at 55% throttle (3750 r.p.m., revolutions per minute) followed by 6 minutes of full throttle (5600 r.p.m.). The test continue for 400 hours or until termination of the test upon engine failure or observation of excessive engine deposit formation. Test results are reported in the following Table:

(16) TABLE-US-00001 Hours to Ex. termination Observation 1 400 Piston cleanliness equal to or better than that of gasoline fueled engine; very little or no wear 3 (comp) 55 Sticky deposits observed in piston grooves; test terminated due to expected premature failure 4 (comp) 50 Failure of engine due to seizure: piston rings stuck, followed by detonation and piston failure

(17) The result show that conventional 2-cycle lubricants do not perform satisfactorily with JP5 fuel, whereas the lubricant of the present invention performs well.

(18) Each of the documents referred to above is incorporated herein by reference. Except in the Examples, or where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are to be understood as modified by the word about. Unless otherwise indicated, each chemical or composition referred to herein should be interpreted as being a commercial grade material which may contain the isomers, byproducts, derivatives, and other such materials which are normally understood to be present in the commercial grade. However, the amount of each chemical component is presented exclusive of any solvent or diluent oil, which may be customarily present in the commercial material, unless otherwise indicated. It is to be understood mount, range, and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the invention can be used together with ranges or amounts for any of the other elements. As used herein, the expression consisting essentially of permits the inclusion of substances that do not materially affect the basic and novel characteristics of the composition under consideration.