Abstract: The disclosed technology relates to corrosion- or rust-preventive coating compositions and methods of their use. The compositions comprise a rust preventative composition, optionally including a diluent, and a quaternary ammonium salt.

Abstract: Provided are octane enhancing additives and methods that improve a liquid fuel composition's octane rating. A liquid fuel composition may comprise a liquid fuel and an octane enhancing additive. The octane enhancing additive may comprise an indoline compound with a bicyclic ring structure, wherein the indoline compound comprises a six-membered aromatic ring and a five-membered aliphatic ring that share a carbon-carbon aromatic bond. The five-membered aliphatic ring may be heterocyclic and may comprise a nitrogen positioned in an alpha position to the six-membered aromatic ring.

Abstract: A method for preparing a fuel composition which comprises a base fuel, an oxygenate and an octane-boosting additive comprises: blending an additised oxygenate with a base fuel, wherein the additised oxygenate comprises an oxygenate and an octane-boosting additive. The method enables suitable amounts of octane-boosting additives to be incorporated into a fuel composition, whilst enabling fuels having a range of properties to be prepared.

Abstract: An additive has been prepared for blending with gasoline that facilitates a cylinder resident reaction, in high compression internal combustion engines (ICEs), to produce an increase in engine's mechanical energy output. A method of increasing mechanical efficiency of an internal combustion engine (ICE) comprising blending an amount of additive with gasoline to perform hydrolysis of olefin hydrocarbons, represented by octene (C8) into petroleum gas hydrocarbons, represented by butane (C4), wherein the additive facilitates cylinder-resident reaction, aided by a low concentration of organometallic catalyst, to utilize the elements of the water combustion product, to hydrolyze olefin hydrocarbons such as octene, resident in the gasoline, into petroleum gas hydrocarbons such as butane, and to increase the ICE's efficiency of utilization of the energy of the fuel.

Abstract: The present disclosure provides fuel additives including a quaternary ammonium salt formed by reacting an alkyl carboxylate with a compound formed from a hydrocarbyl substituted acylating agent reacted with a select amine. Also provided herein are fuel compositions including the novel fuel additives and methods of combusting a fuel including the fuel additives herein. The unique quaternary ammonium salts herein are advantageous because they can be made through a simple alkylation process and provide improved detergency at low treat rates by making available a relatively less sterically hindered quaternary nitrogen for detergency activity in the fuel.

Abstract: In the present spark ignition internal combustion engine, a shortest self-ignition delay time ?min for a maximum cylinder internal pressure Pmax and a maximum cylinder internal temperature Tmax when equivolume combustion is realized is calculated by using a calculation formula which uses a cylinder internal pressure and a cylinder internal temperature to calculate an self-ignition delay time, and a knock limit ignition timing ITA is determined based on the calculated shortest self-ignition delay time.

Abstract: Use in a gas oil fuel composition, which preferably comprises a Fischer-Tropsch derived fuel, of a compound according to formula (I): wherein: R1 to R4 are each independently hydrogen or a C1-10 alkyl group, where such alkyl groups may be the same as or different from one another; and X is a nitrogen- or oxygen-containing group, for the purpose of reducing the cetane number of said fuel composition; preparation of such a fuel composition; and operating a fuel consuming system.

Abstract: A diesel fuel containing a soot dispersant additive which is a grafted and derivatized low molecular weight copolymer of ethylene and at least one C3-C10 alpha monoolefin is provided. Also provided is a method for improving the fuel economy of a diesel engine which comprises operating the diesel engine with a fuel composition comprising (a) a major amount of a diesel fuel and (b) a minor fuel economy improving effective amount of the soot dispersant additive.

Abstract: A process for catalytically cracking aquatic microbial biomass is provided. Aquatic microbial biomass is catalytically cracked over a cracking catalyst at a temperature of at least 450° C. to obtain a product stream. At least one hydrocarbon fraction is separated from the product stream.

Abstract: Use in a gas oil fuel composition, which preferably comprises a Fischer-Tropsch derived fuel, of a compound according to formula (I): wherein: R1 to R4 are each independently hydrogen or a C1-10 alkyl group, where such alkyl groups may be the same as or different from one another; and X is a nitrogen- or oxygen-containing group, for the purpose of reducing the cetane number of said fuel composition; preparation of such a fuel composition; and operating a fuel consuming system.

Abstract: The present disclosure relates to methods and compositions for improving fuel atomization and combustion efficiency comprising fuel additives for use in combustion systems where fuel is injected into the combustion zone under very high pressure

Abstract: A composition and method for improving the performance, and thus, also the fuel economy, of an internal combustion engine by introducing a fuel additive into the engine's fuel supply to enhance fuel lubricity. The composition can feature a mixture of esters, glycol ether, and a solvent. The mixture of esters can include adipate esters, azelate esters, dodecanedioate esters, sebacate esters, or phthalate esters. Esters that may be used to create the composition can include a mixture of two or more adipate esters such as, for example, an adipic acid ester, a glutaric acid ester, and a succinic acid ester. The composition can further feature a smoke suppressant that can be an organometallic soap. The organometallic soap can be an iron salt of a fatty acid such as, for example, ferrocene. The composition can be used as a combustion modifier fuel additive and as a lubricating oil.

Abstract: Fuel additives, fuel formulations, and processes for their preparation and use are provided. The additives improve the combustion properties of hydrocarbon fuels. The enhanced combustion indicates reductions in certain emissions.

Abstract: Disclosed is a stabilized diesel fuel composition comprising a) a diesel fuel with a cetane number less than or equal to 50, b) an effective amount of at least one compound selected from the group consisting of the cetane improvers and c) i) an effective stabilizing amount of at least one compound selected from the group consisting of the stable nitroxide compounds or ii) an effective synergistic stabilizing amount of at least one compound selected from the group consisting of the stable nitroxide compounds and at least one antioxidant compound selected from the group consisting of the aromatic amine antioxidants and the hindered phenolic antioxidants. The cetane improvers are for example nitrate esters. The diesel fuel compositions exhibit improved filterability.

Abstract: Disclosed is a process to make environment friendly components for refinery blending of transportation fuels. The process involves contacting a petroleum distillate with an oxygen-containing gas at oxidation conditions in the presence of a heterogeneous catalyst comprising a Group VII metal on a basic support to oxidize any sulfur and/or nitrogen-containing compounds in the distillate. A portion of these sulfur and/or nitrogen-containing compounds is then removed from the oxidation zone effluent.

Abstract: This invention is a fuel composition having a sulphur content of ?50 ppm by weight and comprising ?50 ppm by weight of at least one fused polycyclic aromatic compound which has at least one hetero-atom selected from O and N either (a) as a heterocyclic group, or, (b) as an exocyclic group in which the hetero-atom is attached either directly or through one other carbon atom to a ring carbon atom wherein the fused polycyclic aromatic compound is substituted on at least one of its ring carbon atoms by a C1-C4 alkyl group. These compounds are capable of improving the antiwear and lubricity properties of a low sulphur fuels, especially diesel fuels, when compared with the performance of the same fuel in the absence of such compounds.

Abstract: The present invention provides a polymeric a fuel composition comprising (i) a fuel; and (ii) a polymeric compound; wherein the polymeric compound comprises at least one monomer unit of Formula I wherein R1 is H or a C1-10 hydrocarbyl group; wherein L is an optional C1-30 hydrocarbyl linker group; and wherein heterocycle is an optionally substituted heterocyclic ring.

Abstract: Injector deposits in a direct injection gasoline engine are reduced by providing as fuel for the operation of said direct injection engine a fuel composition comprising a fuel-soluble compound having the formula (I): wherein R1 and R2 are independently C1-4 alkyl, R3 is a radical of the formula CmH2m wherein m is an integer of 2 to 6, R4 and R5 are each independently (i) hydrogen (ii) C1-4 alkyl, wherein R6 is selected from the group consisting of hydrogen and C1-4 alkyls and R7 is selected from the group consisting of hydrogen and C1-30 alkyl, (iv) wherein R8 is a saturated or unsaturated, linear, branched or cyclic, C7-23 hydrocarbyl group or (v) wherein R4 and R5 together with the nitrogen atom to which they are bonded, form a cyclic ring in which further hetero atoms.

Abstract: A fuel of an emulsion between water and a liquid hydrocarbon. The emulsion is stabilized by adding a polymeric surfactant obtainable by reaction between: (i) a polyolefin oligomer functionalized with at least one group deriving from a dicarboxylic acid, or a derivative thereof; and (ii) a polyoxyalkylene of linear oxyalkylene units. The polyoxyalkylene is linked to a long-chain alkyl group optionally containing one or more ethylenic unsaturations. The fuel has high stability over time, without forming carbonaceous deposits which adhere to metal surfaces.

Abstract: A method of suppressing particulate emissions during fuel combustion comprising the steps of providing a fuel, and adding to the fuel a heterocyclic hydrocarbon structure comprising at least one nitrogen atom.

Abstract: A method of improving the compatibility of a fuel additive composition comprising blending together the following components: a) a Mannich condensation product of (1) a high molecular weight alkyl-substituted hydroxyaromatic compound, (2) an amine having the formula:  wherein A is CH or nitrogen, R1, R2, R3 are independently hydrogen or lower alkyl of 1 to about 6 carbon atoms and each R2 and R3 is independently selected in each —CR2R3— unit, and x is an integer from 1 to about 6;  and (3) an aldehyde, wherein the respective molar ratio of reactants (1), (2), and (3) is 1:0.1-2:0.1-2; b) a hydrocarbyl-terminated poly(oxyalkylene) monool; c) a carboxylic acid as represented by the formula: R4(COOH)y  wherein R4 represents a hydrocarbyl group having about 2 to about 50 carbon atoms, and y represents an integer of 1 to about 4; and d) an anhydride selected from the group consisting of succinic, glutaric, phthalic, and alkyl anhydrides.

Abstract: The present invention relates to additives for enhancing the lubricity of hydrocarbon fuel oils, the inventive additive composition including one or more of the reaction products of (i) an alkylated polyamine and (ii) urea or isocyanate, or the salt adducts of these reaction products. More particularly, the present invention provides for a process for improving the lubricity of hydrocarbon fuel oils, which are low in inherent lubricity due to treatment to reduce sulfur and aromatic components for improved emissions.

Abstract: There is provided use of a thermal stabiliser for increasing the thermal stability of a cetane improver in a fuel composition comprising (i) a fuel, and (ii) the cetane improver wherein the thermal stabiliser is a compound of the formula H—R1 wherein H is a group comprising a heterocyclic group and R1 is a hydrocarbyl group having from 10 to 200 carbons.

Abstract: This invention provides a fuel composition having a sulphur content of not more than 50 ppm by weight and comprising at least 50 ppm based on the total weight of the fuel composition of at least one fused polycyclic aromatic compound which comprises at least one exocyclic group containing nitrogen wherein the nitrogen is attached directly to a ring carbon atom. Specific examples of such compounds include 1-amino naphthalene, 1,8-diaminonaphthalene, or 5-aminoindole, 2-(2-aminophenyl)indole and 8-aminoquinoline. These compounds are capable of improving the antiwear and lubricity properties of a low sulphur fuel when compared with that of the same fuel in the absence of such compounds.

Abstract: The invention provides photoluminescent markers consisting essentially of fluorene copolymers, which are colorless or nearly colorless to the naked eye and exhibit strong photoluminescence between about 380-800 nm upon exposure to ultra-violet radiation or laser light. The soluble fluorene copolymers described in this invention having a general formula as shown in Formula 1.

Abstract: This invention is a fuel composition having a sulphur content of ≦50 ppm by weight and comprising ≧50 ppm by weight of at least one fused polycyclic aromatic compound which has at least one hetero-atom selected from O and N either (a) as a heterocyclic group, or, (b) as an exocyclic group in which the hetero-atom is attached either directly or through one other carbon atom to a ring carbon atom wherein the fused polycyclic aromatic compound is substituted on at least one of its ring carbon atoms by a C1-C4 alkyl group. These compounds are capable of improving the antiwear and lubricity properties of a low sulphur fuels, especially diesel fuels, when compared with the performance of the same fuel in the absence of such compounds.

Abstract: Ethers of polyalkyl or polyalkenyl N-hydroxyalkyl succinimides having the formula: or a fuel soluble salt thereof; wherein R is a polyalkyl or polyalkenyl group having an average molecular weight in the range of about 450 to about 5,000; n is an integer from 2 to 5; and Z is a moiety selected from the group consisting of  wherein R1 is a hydroxy, nitro, cyano or —(CH2)x—NR3R4, wherein R3 and R4 are independently hydrogen or lower alkyl of 1 to 6 carbon atoms and x is 0 or 1; and R2 is hydrogen, hydroxy, nitro, cyano or —(CH2)y—NR5R6, wherein R5 and R6 are independently hydrogen or lower alkyl of 1 to 6 carbon atoms and y is 0 or 1. The compounds of formula I are useful as fuel additives for the prevention and control of engine deposits.

Abstract: The invention concerns a fuel for diesel engines, with a sulphur content of less than 500 ppm containing in a major proportion at least one average distillate from a straight-run distilling cup of crude oil, with temperature ranges between 150 and 400° C. and in a minor proportion a lubricating additive containing monocarboxylic and polycyclic acids.

Abstract: The lubricity (anti-wear properties) of fuels, for example hydrocarbon fuels, oxygenated fuels or mixtures thereof, particularly diesel or aviation fuels having reduced sulphur and/or aromatic content for compliance with regulator requirements, is improved by addition of at least a product which can be obtained by reacting components a), b) and c), where component a) is a compound of the formula I or a mixture of compounds of the formula I, component b) is a compound of the formula II or a mixture of compounds of the formula II and component c) is a compound of the formula III or a mixture of compounds of the formula III, in which the general symbols are as defined in claim 1, the compound of the formula I being, for example, pentaerythritol, thiodiethylene glycol, 1,4-butanediol, 1,4-propanediol, diethylene glycol, triethylene glycol, diethanolamine or glycerol, the compound of the formula II being, for example, sunflower oil or coconut fat, and the compound of the formula III being, for ex

Abstract: Gasoline additives of the present invention comprise nitrogen-containing compounds obtained by hydrolyzing a polyoxyalkylene glycol derivative resulting from polymerization of an epoxy compound using a suitable ketimine compound as a reaction initiator or by modifying the terminal ends of a polybutene compound with amine. Blending the inventive gasoline additive to a base gasoline can produce a gasoline composition which is suitable for use in direct injection gasoline engine.

Abstract: A poly(oxyalkylene)pyridyl or piperidyl ether having the formula: wherein A is a nitrogen-containing ring selected from the group consisting of 3-pyridyl, 4-pyridyl, 3-piperidyl and 4-piperidyl; R1 and R2 are independently hydrogen or lower alkyl and each R1 and R2 is independently selected in each —O—CHR1—CHR2— unit; R3 is hydrogen, alkyl having 1 to about 100 carbon atoms, phenyl, aralkyl having about 7 to about 100 carbon atoms or alkaryl having about 7 to about 100 carbon atoms; n is an integer from about 5 to about 100; and x is an integer from 0 to 4. The poly(oxyalkylene)pyridyl and piperidyl ethers of the present invention are useful as fuel additives for the prevention and control of engine deposits.

Abstract: A poly(oxyalkylene)pyridyl or piperidyl ester having the formula: ##STR1## or a fuel-soluble salt thereof; wherein A is a nitrogen-containing ring selected from the group consisting of 3-pyridyl, 4-pyridyl, 3-piperidyl and 4-piperidyl; R.sub.1 and R.sub.2 are independently hydrogen or lower alkyl having 1 to about 6 carbon atoms and each R.sub.1 and R.sub.2 is independently selected in each --O--CHR.sub.1 --CHR.sub.2 -- unit; R.sub.3 is hydrogen, alkyl having 1 to about 100 carbon atoms, phenyl, aralkyl having about 7 to about 100 carbon atoms or alkaryl having about 7 to about 100 carbon atoms; x is an integer from 0 to 4; and n is an integer from about 5 to about 100.The poly(oxyalkylene)pyridyl and piperidyl esters of the present invention are useful as fuel additives for the prevention and control of engine deposits.

Abstract: Esters of polyalkyl or polyalkenyl N hydroxyalkyl succinimides having the formula: ##STR1## or a fuel soluble salt thereof; wherein R is a polyalkyl or polyalkenyl group having an average molecular weight in the range of about 450 to about 5,000;n is an integer from 2 to 5; and Z is a moiety selected from the group consisting of ##STR2## wherein R.sub.1 is a hydroxy, nitro, cyano or --(CH.sub.2).sub.x --NR.sub.3 R.sub.4, wherein R.sub.3 and R.sub.4 are independently hydrogen or lower alkyl of 1 to 6 carbon atoms and x is 0 or 1; and R.sub.2 is hydrogen, hydroxy, nitro, cyano or --(CH.sub.2).sub.y --NR.sub.5 R.sub.6, wherein R.sub.5 and R.sub.6 are independently hydrogen or lower alkyl of 1 to 6 carbon atoms and y is 0 or 1.The compounds of formula I are useful as fuel additives for the prevention and control of engine deposits.

Abstract: Pyridyl and piperidyl esters of polyalkylphenoxyalkanols having the formula: ##STR1## or a fuel soluble salt thereof, wherein A is selected from the group consisting of 3-pyridyl, 4-pyridyl, 3-piperidyl, and 4-piperidyl;R.sub.1 is a polyalkyl group having an average molecular weight in the range of from about 450 to 5,000; andR.sub.2 and R.sub.3 are independently hydrogen or lower alkyl having from about 1 to 6 carbon atoms.The compounds of formula I are useful as fuel additives for the prevention and control of engine deposits.

Abstract: The present invention is directed to the use of cyclic amide alkoxylate compounds as additives in fuel compositions having a major amount of a mixture of hydrocarbons in the gasoline boiling range and a minor amount of one or more cyclic amide alkoxylate compounds of the formula: ##STR1## wherein x is from 2 to 20 and y is from 1 to 50. R.sub.1 and R.sub.2 are independently hydrogen or hydrocarbyl of 1 to 100 carbon atoms. R.sub.3 is hydrocarbyl of 1 to 100 carbon atoms and R.sub.4 is independently hydrocarbyl of 2 to 100 carbon atoms. R.sub.5 is hydrogen, hydrocarbyl of 1 to 100 carbon atoms or acyl of 1 to 20 carbon atoms.The invention is also directed to the use of these cyclic amide alkoxylate compounds for decreasing intake valve deposits, controlling octane requirement increases and reducing octane requirement. The invention is further directed to novel cyclic amide alkoxylate compounds.

Abstract: A fuel additive which comprises an amide compound of the formula ##STR1## wherein R.sup.1 is hydrogen or a C.sub.1 -C.sub.30 hydrocarbon group, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 each are selected from the group consisting of hydrogen, a C.sub.1 -C.sub.10 hydrocarbon group and a group of formula (II), provided that at least one of R.sup.2, R.sup.3, R.sup.4 and R.sup.5 group of formula (II) R.sup.6 is a C.sub.2 -C.sub.6 alkylene group, R.sup.7 is a C.sub.1 -C.sub.6 alkylene group, a is an integer of 1-100, b is an integer of 0-100, the sum of a and b being equal to 1-200, c is an integer of 1-3, d is an integer of 0-2, the sum of c and d being equal to 3, and X is selected from the group consisting of hydrogen, a C.sub.1 -C.sub.30 hydrocarbon group, a group of formula (III), and a group of formula (IV), wherein formulas (II), (III) and (IV) are defined in the disclosure.

Abstract: A fuel additive comprising a urethane compound. A gasoline composition comprising gasoline blended with a urethane compound to suppress sludge or deposits in fuel intake systems or combustion chambers, such as an automobile engine.

Abstract: The use of nitroxide compounds alone or in combination with aromatic amines, such as substituted phenylenediamines, or phenolic antioxidants provides an effective way to prevent oxidative degradation and gum formation in gasolines, especially unstable coker and pyrolysis gasolines.

Abstract: The present invention is directed to the use of multiple cyclic nitrogen-containing alkoxylate compounds as additives in fuel compositions. The invention is also directed to the use of these multiple cyclic nitrogen-containing alkoxylate compounds for decreasing intake valve deposits, controlling octane requirement increases and reducing octane requirement. The invention is further directed to a class of multiple cyclic nitrogen-containing alkoxylate compounds.

Abstract: Polyisobutylsuccinic anhydrides having an average molar ratio of succinic anhydride groups to polyisobutyl groups of from 1.05:1 to 1.3:1 are prepared by reacting polyisobutene having an average molecular weight M.sub.w of 600-5000 and containing at least 70% of terminal double bonds with maleic anhydride in a molar ratio of maleic anhydride to polyisobutene of from 1.05:1 to 3:1 at 160.degree.-210.degree. C. in the presence of a catalytic amount of a dicarboxylic acid of 2 to 6 carbon atoms.

Abstract: The novel polymers of the present invention are prepared by reacting a heterocyclic nitrogen compound containing at least one --N(H)-- group in the ring, an aldehyde and amino-substituted polymer (e.g., an ethylene alpha-olefin interpolymer substituted by primary amino or secondary amino groups) to form an oil soluble Mannich base derivative useful as antioxidant additive in oleaginous compositions such as lubricating oils and fuels. Preferred heterocyclic nitrogen compound are azoles such as benzotriazoles and alkyl-substituted benzotriazoles. Preferred amino-substituted interpolymers comprise amino-substituted ethylene propylene norbornene terpolymers. The polymers of this invention are oil soluble and are useful as dispersants, viscosity index improver dispersants, and as antiwear and antioxidant additives in oleaginous compositions.

Abstract: Various heterocyclic compounds have been discovered that impart improved fuel economy and friction modification to lubricant and fuel compositions. These heterocyclic compounds of the invention preferably contain nitrogen and may be further reacted with hydrocarbyl carboxylic acid acylating reactants or hydrocarbyl phenolic reactants to give higher molecular materials. These higher molecular weight materials have higher oil-solubility and impart dispersancy properties to lubricant and fuel compositions.

Abstract: Sediment and color formation in distillate fuels are reduced by the addition of a quaternary ammonium compound comprising a cation in which the ratio of carbon atoms to quaternary nitrogen atoms is not more than 10:1 and an anion which is derived from an acid which is a carboxylic acid, carboxylic acid anhydride, phenol, sulphurized phenol or sulphonic acid.

Abstract: Disclosed is a fuel composition comprising a hydrocarbon boiling in the gasoline or diesel range and from about 30 to about 5,000 parts per million of an alkylphenyl poly(oxypropylene) aminocarbamate having at least one basic nitrogen and an average molecular weight of about 600 to 6,000 and wherein the alkyl group is substantially straight-chain of at least 15 carbon atoms. The instant invention is based on the discovery that use of the unique hydrocarbyl group, i.e., an alkylphenyl group wherein the alkyl group is derived from a substantially straight-chain alkyl group of at least 15 carbon atoms imparts to the alkylphenyl poly(oxypropylene) aminocarbamate not only lubricating oil compatibility but also an unexpected decrease in crankcase deposits.

Abstract: Hydrogen sulfide evolution in a heavy hydrocarbon (such as a residual fuel oil) derived from a heavy crude oil (such as a API 8 gravity crude) is suppressed by contacting the hydrocarbon with a compound corresponding to the reaction product of a heterocyclic aldehyde (such as furfural) and an organic primary amine.

Abstract: Products of reaction between 1-alkyl-N,N-dialkyl ethanolamines and copolymers of maleic anhydride are new additives which are effective in lowering the cloud point of distillate fuels.

Abstract: Hydrogen sulfide gas evolution from water or hydrocarbons, especially during storage or transport of petroleum residua is suppressed by the incorporation of an effective amount of a diamine of the formula ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are independently an alky radical containing 1 to 14 carbon atoms, (CH.sub.2).sub.n --OR.sub.6 or cycloalkyl containing 5 or 6 carbon atoms and R.sub.5 is hydrogen or methyl. R.sub.1 and R.sub.2 and R.sub.3 and R.sub.4 can be alkylene groups joined together with their respective adjacent N to form a heterocyclic ring. R.sub.6 is hydrogen or an alkyl radical having 1 to 5 carbon atoms and n is an integer of 1 to 5.

Abstract: A stable middle distillate fuel-oil composition which comprises(a) a major portion of a middle distillate fuel-oil; and(b) a minor amount, as storage stabilizing additive, of a N-2-pyridyl succinimide of a copolymer and maleic anhydride graft.

Abstract: Oxidative stability of gasoline mixtures is improved by adding to the gasoline an alkyl 1,2-dihydroquinoline compound, dimer, trimer or polymer thereof. Optionally, a hindered phenol may be conjointly used with the quinoline compound.

Abstract: A distillate fuel, particularly one which has a high acid number initially or which develops a high acid number as a result of fuel degradation, stabilized with a diaminomethane of the formula: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 may be independently a saturated or unsaturated hydrocarbon group, e.g., alkyl, aryl, aralkyl, alkaryl, cycloalkyl, alkenyl, aralkenyl, alkenylaryl, cycloalkenyl and the like or heterocyclyl groups and in which R.sub.1 and R.sub.2 and/or R.sub.3 and R.sub.4 may be joined together to form a five or six member heterocyclyl ring and R.sub.5 may be hydrogen or lower alkyl is disclosed. A method of stabilizing a fuel oil wherein a stabilizing amount of the above-mentioned diaminomethane is incorporated into the fuel oil is also disclosed.