Motor fuel composition
Moore et al.  
 [ 1 MOTOR FUEL COMPOSITION [75] V Inventors: Fred W. Moore, Fishkill; Herbert E.  
 Vermillion, Wappingers Falls, both of N.Y.  
 [73] Assignee: Texaco Inc., New York, NY,  
 [22] Filed: Mar. 6, 1969 [21] Appl. No.: 804,978  
 [52] US. Cl. 44/58 [51] Int. Cl C101 1/10 [58] Field of Search 44/58 [56] References Cited UNITED STATES PATENTS 2,965,458 12/1960 Sawyer et a1. 44/58 3,020,134 2/1962 Keller et a1. 44/58 3,031,278 4/1962 Buckmann et a1 44/58 3,035,905 5/1962 Keller 44/58 3,235,494 2/1966 Piatt et a1. 44/58 X Apr. 15, 1975 3,326,801 6/1967 SChlObOhm et al. 44/58 X 3,751,235 3/1973 Schoen 44/58 FOREIGN PATENTS OR APPLICATIONS 683,197 11/1952 United Kingdom 44/58 Primary Examiner-Winston A. Douglas Assistant Examiner-W. J. Shine Attorney, Agent, or FirmT. H. Whaley; C. G. Ries [57] ABSTRACT Motor fuel composition comprising a mixture of hydrocarbons in the gasoline boiling range containing 0.03 to 1.0 volume percent of a paraffinic oil fraction consisting of at least 55 percent of paraffinic hydrocarbons and less than 16 percent of aromatic hydrocarbons and having an average molecular weight in the range from 540 to 850, and method of preventing a deposits build-up in a gasoline engine.  
 8 Claims, No Drawings MOTOR FUEL COMPOSITION This invention relates to a motor fuel composition for a four-cycle, spark-ignited internal combustion engine. More particularly, the invention relates to a motor fuel composition containing a selected high-boiling mineral oil fraction in an amount effective to reduce or eliminate the formation of harmful deposits on the intake valves and around the intake ports of an internal combustion engine.  
  Internal combustion engines, particularly of the overhead valve design, are subject to a substantial build-up of hard, tenacious deposits on the intake valves and ports of the engine. These deposits interfere with the operation of the fuel intake system. As the deposits level grows, the engine exhibits loss of power, rough idling and, occasionally, valve burning. When the deposits become excessive, portions break off and are drawn into the combustion chamber. Instances of mechanical damage to the piston and piston rings caused by these deposits have been observed.  
  Considerable work has been conducted to determine the nature and cause of the intake valve deposits. The deposits themselves are composed essentially of the byproducts of fuel combustion and lubricating oil deterioration. Analysis of the deposits indicates that the viscosity index improvers contained in the lubricating oil act as binders for the deposits. Polymethacrylate viscosity index improvers, as an example, are one&#39;class of materials which appear to contribute materially to the deposits build-up.  
  An understanding of engine operation will show how lubricating oil deterioration can contribute to deposits in the fuel intake system. A spark-ignited internal combustion engine contains a reservoir of lubricating oil in the crankcase. When the engine is in operation. the greater part of the crankcase oil is splashed up on the operating parts of the engine and on the cylinder walls. A portion of this oil, however, is pumped under pressure to the upper parts of the engine to lubricate the working parts therein. In an overhead valve engine, a small stream of the oil pumped to the upper section of the engine is constantly run down the intake and exhaust valve stems to insure that they are constantly lubricated in their guides during operation. The oil trickling down the intake valve stem, the valve head and around the intake port is apparently pyrolyzed under the temperatures prevailing, thereby contributing to the formation and build-up of the above-noted deposits.  
  This particular problem is not encountered to any material extent in the exhaust mmanifold or around the exhaust ports or valves. This is believed to be due to the high temperatures existing in the exhaust manifold and to the action of the expelled exhaust gases which do not permit the laydown of deposits or continually burns and carries off any potential deposits.  
  Gasolines containing a minor amount of a distillate mineral oil as an upper cylinder lubricant or top oiler&#34; are well known. In general, the upper cylinder lubricants employed in gasoline have been light distillate mineral oils as opposed to heavier lubricating oil fractions. Indeed, the latter have generally been found to be harmful from the viewpoint of deposit formation in the combustion chamber. A top cylinder lubricating oil commercially employed in a premium gasoline is characterized as a highly refined distillate lubricating oil fraction having an average molecular weight of about 300 and a 50 percent distillation point of about 700F.  
  It has now been discovered that a minor amount of certain highly refined, high boiling, paraffinic lubricating oil fractions dissolved in a motor fuel composition is effective for preventing the formation of deposits on the intake valves and ports of a four-cycle, sparkignited, internal combustion engine. More specifically, a motor fuel composition comprising a mixture of hydrocarbons boiling in the gasoline boiling range containing from about 0.03 to [.0 volume percent ofa paraffinic mineral oil fraction consisting of at least 55 percent of paraffinic hydrocarbons and less than 16 percent of aromatic hydrocarbons and having an average molecular weight in the range from 540 to 850 is effective for preventing the aforesaid deposits. These oil fractions can also be characterized by their 50 percent distillation point which is at a temperature of at least 940F. or higher.  
  Average molecular weight as employed herein refers to molecular weight determination by the ASTM Osmometer Method under ASTM number D250367.  
  The nature of the mineral oil fraction effective to provide a gasoline composition having the property of preventing intake valve and port deposits in a gasoline engine is critical. In general, only a refined paraffinic mineral oil fraction of lubricating oil quality consisting of at least 55 percent and up to 100 percent paraffinic hydrocarbons and less than 16 percent of aromatic hydrocarbons, the fraction having an average molecular weight in the range 540 to 850 is effective for the purpose described. The preferred oils are those consisting of 60 to 100 percent paraffinic hydrocarbons and less than 7 percent of aromatic hydrocarbons having an average molecular weight in the range of 600 to 800. Particularly preferred oils are those consisting of 60 to percent of paraffinic hydrocarbons and less than 7 percent aromatic hydrocarbons. These oil fractions characteristically have a.50 percent distillation point of at least 940F. or higher and, more specifically, in the range of 950 to l lOOF.  
  Light lubricating oil fractions having molecular weights below the critical range are ineffective in this invention. These ineffective oils also have a 50 percent distillation pointbelow about 875F. Non-paraffinic lubricating oil fractions are also ineffective in this invention and, in addition, result in prohibitively high deposits formation in the combustion chamber of the car engme.  
  The base fuel of the invention comprises a mixture of hydrocarbons boiling in the gasoline boiling range. This base fuel may consist of straight chain or branched chain paraffins, cyclo-paraffins, olefins and aromatic hydrocarbons or any mixture of these. This fuel can be derived from straight run naphtha, polymer gasoline, natural gasoline or from catalytically cracked or thermally cracked hydrocarbons and catalytically reformed stocks. The composition of the base fuel is not critical nor does the octane level of the base fuel have any material effect on the invention. Any conventional motor fuel base may be employed in the practice of this invention.  
  The base fuel may contain any of the additives normally employed in a motor fuel. For example, the base fuel may contain an anti-knock compound, such as a tetraalkyllead compound including tetraethyllead, tetramethyllead, tetrabutyllead, mixtures thereof and the like. The tetraalkyllead mixture commercially available for automotive use contains an ethylene chlorideethylene bromide mixture as a scavenger for removing lead from the combustion chamber in the form of a volatile lead halide. The tetraalkyllead mixtures are generally employed in gasoline in a concentration ranging from about 0.5 to 4.0 cc. of the mixture per gallon of gasoline. Other conventional additives for this gasoline, including anti-icing agents, corrosion inhibitors, dyes, carburetor detergents, deposit modifiers, multipurpose additives and the like, are illustrated by the following US Pat. No. 2,632,695, 2,844,449, 3,325,260, 3,232,724, 2,622,018 and 2,922,708.  
  The novel fuel composition of the invention is prepared by mixing a suitable amount of a suitable paraffinic mineral oil fraction to the base gasoline. The minimum amount of additive employed in the fuel composition is critical in order to realize the benefits of the invention. Broadly, the additive must be employed in a range from about 0.03 to 1.0 volume percent. Highly effective results have been realized when the additive was employed in amounts from about 0.05 to 050 volume percent of the fuel composition. The preferred concentration of the additive is an amount from about 0.06 to 0.25 volume percent.  
  The test employed for testing the fuel compositions was the Buick Induction System Deposits Test conducted using a 1964 Buick 425 CID V-8 engine. The fuels employed in the tests were evaluated basis deposit ratings of the intake valves and ports of the engine as more fully described below.  
  The test is conducted using the noted engine equipped with a PCV (Positive Crankcase Ventilation) valve and installed on a dynamometer test stand with supporting equipment to control speed, load and engine temperatures. This test requires approximately 350 gallons of fuel and 4 gallons of lubricant per run.  
  Prior to each run, the cylinder heads are completely reconditioned and new intake valves installed. Special care must be taken to insure that the inlet valve-tovalve guide clearance be maintained between 0.0035 to 0.0045 inches. In addition, the valve seat widths are maintained between 3/64 and 5/64 inches. The engine block is completely overhauled in accordance with the procedures stated in the 1964 Buick Service Manual when blow-by or oil consumption become excessive.  
  The engine is charged with four quarts of oil and flushed for minutes at 1500 rpm. Following an oil drain, four quarts of new oil are added and the fuel tests begun. The engine is operated on a four-stage-six-hour cycle for a total of 16 cycles or 96 hours as follows:  
 -Continued State Cycle Time Hours Operation Temp.. F. Ckc&#39;s Oil 200 234 t 2 234 i 2 Temp, F.  
 &#34;Typical values, not controlled. &#34;Approximate values-spark advance set 6BTDC at 600 rpm.  
  Upon completion of a run, the cylinder heads and valves are removed and the valves visually rated for the extent of deposit build-up on the valve tulip surface. The intake valve deposits are rated according to a merit rating scale running from 10 to l. A rating of 10 indicates a perfectly clean valve while the rating of l is applied to an extremely heavily coated valve. Deposits around the port opening are rated T-trace, L-light, M- medium and H-heavy.  
  The following examples illustrate the practice of this invention. The examples give the characteristics of the mineral oil fraction which was blended into the base gasoline to formulate the fuel composition of the invention. The oils were blended with the base gasoline in the proportions indicated in volume percent basis the total fuel composition, the balance eing the base fuel.  
  The base fuel was a typical premium grade gasoline containing about 3 cc. of tetraethyllead per gallon. This base fuel consisted of 25 percent aromatic, 14.5 percent olefinic and 60.5 percent aliphatic hydrocarbons as determined by FIA analysis. This gasoline had an ASTM distillation IBP of F, an ER of 380F. and a Research Octane Number of about 101.3.  
  A typical commercial gasoline without the additive of the invention gave an intake valve rating of about 6.0 and a port rating of heavy. An improvement in the valve rating of 0.5 units above the base fuel and an acceptable port rating, Trace of Light, is a significant improvement. An improvement of 1 .0 unit or more generally to 7.0 or above and a passing port rating is a very substantial improvement in engine cleanliness.  
 EXAMPLE I.  
  A distillate paraffinic oil fraction of lubricating quality having an average molecular weight of 604, a 50 percent distillation point of 1005F., and consisting of 64.1 percent paraffinic hydrocarbons and 3.8 percent of aromatic hydrocarbons.  
 EXAMPLE 2.  
  The 50 percent bottoms from the distillation of the oil in Example 1 having an average molecular weight of 670, a 50 percent distillation point of l050F. and consisting of 63.7 percent paraffinic hydrocarbons and 4.9 percent aromatic hydrocarbons.  
 EXAMPLE 3.  
  A highly refined residual paraffmic oil fraction of lubricating quality having an average molecular weight of 623, a 50 percent distillation point of 1026F., and consisting of 68.5 percent paraffinic hydrocarbons and 6.2 percent aromatic hydrocarbons.  
 EXAMPLE 4.  
  A moderately refined residual paraffinic oil fraction of lubricating quality having an average molecular weight of 670, a 50 percent distillation point of 1042F., and consisting of 62.8 percent paraffinic hydrocarbons and 8.4 percent aromatic hydrocarbons.  
  EXAMPLE 5.  
  A distillate paraffinic oil fraction of lubricating quality having an average molecular weight of 544. a 50 percent distillation point of 967F.. and consisting of 63 percent paraffinic hydrocarbons and 3 percent aromatic hydrocarbons.  
 EXAMPLE 6.  
  A highly refined residual paraffinic oil fraction of lubricating quality having an average molecular weight of 712, a 50 percent distillation point of 1086F., and consisting of 70.5 percent paraffinic hydrocarbons and 5.8 percent aromatic hydrocarbons.  
 EXAMPLE 7.  
  A highly refined residual paraffinic oil fraction of lubricating quality having an average molecular weight of 734, a 50 percent distillation point of 1049F., and consisting of 66.7 percent of paraffmic hydrocarbons and 4.1 percent of aromatic hydrocarbons.  
 EXAMPLE 8.  
  A moderately refined residual paraffinic oil fraction of lubricating quality having an average molecular weight of 754, a 50 percent distillation point of 1086F., and and consisting of 65.3 percent of paraffinic hydrocarbons and 15.6 percent of aromatic hydrocarbons.  
 EXAMPLE 9.  
  A distillate naphthenic oil fraction of lubricating quality having an average molecular weight of 425, a 50 percent distillation point of 857F.. and consisting of 44 percent paraffinic hydrocarbons and 19.5 percent of aromatic hydrocarbons.  
 EXAMPLE 10.  
  A distillate paraffinic oil fraction of lubricating quality having an average molecular weight of 454, a 50 percent distillation point of 865F., and consisting of 62.3 percent paraffinic hydrocarbons and 2.3 percent of aromatic hydrocarbons.  
 EXAMPLE 11.  
  A distillate paraffinic oil fraction of lubricating quality having an average molecular weight of 430, a 50 percent distillation point of about 850F., and consisting of 61.6 percent paraffinic hydrocarbons and 0 percent of aromatic hydrocarbons.  
 EXAMPLE 12.  
  A hydrotreated, cracked distillate oil fraction having an average molecular Weight of about 210, a 50 percent distillation point of 609F., and consisting of 38.2 percent paraffinic hydrocarbons and 41.5 percent of aromatic hydrocarbons.  
 EXAMPLE 13.  
 Table 1 Buick Induction System Deposits Test Oil Concentration Valve Port Fuel Composition Vol. Percent Rating Rating Base fuel None 6.0 H Example 1 a 0.10 7.6 T b 0.16 7.8 T c 0.20 8.4 T d 0.32 9.0 T Example 2 0.16 8.7 T Example 3 a 0.50 9.0 L b 0.075 8.3 T c 0.15 8.5 L d 0.05 7.1 L Example 4 0.50 9.0 L Example 5 0.50 7.6 L Example 6 0.16 9.0 T Example 7 0.15 8.2 T Example 8 0.15 8.1 L Example 9 0.25 6.3 H Example 10 0.50 5.7 H Example 1 l 0.30 6.3 H Example 12 0.50 6.0 M Example 13 0.50 6.3 H  
  Examples 1 through 8, inclusive, are representative of the present invention and show surprising cleanliness of the engine intake valves and ports in this test. The fuel compositions of Examples 9 through 13, which contain oils outside the specifically effective group. show little or no improvement in this test or actually increased intake valve and port fouling.  
  Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.  
 We claim:  
  1. A motor fuel composition comprising a mixture of hydrocarbons in the gasoline boiling range containing from about 0.03 to 1.0 volume percent of a highly refined paraffinic oil fraction of lubricating oil quality consisting of 60 to 100 percent of paraffmic hydrocarbons and less than 7 percent of aromatic hydrocarbons, said fraction having an average molecular weight in range of 600 to 800 and a 50 percent distillation point in a range of 950 to 1100F.  
  2. A motor fuel composition according to claim 1, containing from about 0.05 to 0.5. volume percent of said paraffinic oil fraction.  
  3. A motor fuel composition according to claim 1 containing from about 0.06 to 0.25 volume percent of said paraffmic oil fraction (and said fraction consists of 60 to percent of paraffinic hydrocarbon).  
  4. A motor fuel composition according to claim 1 in which said composition contains from (0.075) 0.06 to 0.25 volume percent of said paraffmic oil fraction, said -fraction being characterized by consisting of 60 to 75 percent of paraffinic hydrocarbons and less than 7 percent of aromatic hydrocarbons having an average molecular weight in the range of 600 to 800 and having a 50 percent distillation point in the range of 950 to l F).  
  5. A motor fuel composition according to claim 1, containing from about 0.5 to 4.0 cc. of a tetraalkyllead antiknock compound per gallon.  
  6. A motor fuel composition according to claim 1 in which said paraffinic oil portion has an average molecular weight of 604, a 50 percent distillation point of 1005F and consists of 64.1 percent paraffmic hydrocarbons and 3.8 percent of aromatic hydrocarbons.  
 of hydrocarbons in the gasoline boiling range containing from about 0.03 to 1.0 volume percent of a paraflinic oil fraction of lubricating oil quality consisting of 60 to percent of paraffinic hydrocarbons and less than 7 percent of aromatic hydrocarbons, said fraction having an average molecular weight in the range of 600 to 800 and a 50 percent distillation point in a range of