QUATERNARY AMMONIUM COMPOUNDS AND THEIR USE AS FUEL OR LUBRICANT ADDITIVES

Abstract

A quaternary ammonium salt of formula wherein each of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 is independently selected from an optionally substituted alkyl, alkenyl or aryl group having less than 8 carbon atoms and R.sup.5 is hydrogen or an optionally substituted hydrocarbyl group.

##STR00001##

Claims

1. A quaternary ammonium salt of formula: ##STR00016## wherein each R.sub.1, R.sup.2, R.sup.3 and R.sup.4 is independently selected from an optionally substituted alkyl, alkenyl or aryl group having less than 8 carbon atoms and R.sup.5 is hydrogen or an optionally substituted hydrocarbyl group.

2. A quaternary ammonium salt according to claim 1 which is the reaction product of a tertiary amine of formula R.sup.1R.sup.2R.sup.3N with a quaternising agent selected from: (i) an ester of formula R.sup.5COOR.sup.4; (ii) a carbonate compound of formula R.sup.0OCOOR.sup.4 and then a carboxylic acid of formula R.sup.5COOH; and (iii) an epoxide having less than 8 carbon atoms and a carboxylic acid of formula R.sup.5COOH; wherein R.sup.0 is an optionally substituted hydrocarbyl group.

3. A quaternary ammonium salt according to claim 2 which is the reaction product of: (a) a tertiary amine of formula R.sup.1R.sup.2R.sup.3N; (b) an epoxide having less than 8 carbon atoms; and (c) a carboxylic acid of formula R.sup.5COOH.

4. A method of preparing a quaternary ammonium salt, the method comprising reacting (a) a tertiary amine of formula R.sup.1R.sup.2R.sup.3N with (b) an acid-activated alkylating agent in the presence of (c) a carboxylic acid of formula R.sup.5COOH.

5. An additive composition comprising one or more quaternary ammonium compounds as claimed in claim 1 and a diluent or carrier.

6. A lubricating composition comprising as an additive one or more quaternary ammonium compounds as defined in claim 1.

7. A fuel composition comprising as an additive one or more quaternary ammonium compounds as defined in claim 1.

8. A fuel composition according to claim 7 wherein the fuel is diesel fuel.

9. A fuel composition according to claim 8 which comprises one or more further detergents selected from: (i) an additional quaternary ammonium salt additive which is not a quaternary ammonium salt of formula: ##STR00017## wherein each of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 is independently selected from an optionally substituted alkyl, alkenyl or aryl group having less than 8 carbon atoms and R.sup.5 is hydrogen or an optionally substituted hydrocarbyl group; (ii) the product of a Mannich reaction between an aldehyde, an amine and an optionally substituted phenol; (iii) the reaction product of a carboxylic acid-derived acylating agent and an amine; (iv) the reaction product of a carboxylic acid-derived acylating agent and hydrazine; (v) a salt formed by the reaction of a carboxylic acid with di-n-butylamine or tri-n-butylamine; (vi) the reaction product of a hydrocarbyl-substituted dicarboxylic acid or anhydride and an amine compound or salt which product comprises at least one amino triazole group; and (vii) a substituted polyaromatic detergent additive.

10. A fuel composition according to claim 7 wherein the fuel is gasoline fuel.

11. A fuel composition according to claim 10 which comprises one or more gasoline detergents selected from: (p) hydrocarbyl-substituted polyoxyalkylene amines or polyetheramines; (q) acylated nitrogen compounds which are the reaction product of a carboxylic acid-derived acylating agent and an amine; (r) hydrocarbyl-substituted amines wherein the hydrocarbyl substituent is substantially aliphatic and contains at least 8 carbon atoms; (s) Mannich base additives comprising nitrogen-containing condensates of a phenol, aldehyde and primary or secondary amine; (t) aromatic esters of a polyalkylphenoxyalkanol; (u) an additional quaternary ammonium salt additive which is not a quaternary ammonium salt of formula: ##STR00018## wherein each of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 is independently selected from an optionally substituted alkyl, alkenyl or aryl group having less than 8 carbon atoms and R.sup.5 is hydrogen or an optionally substituted hydrocarbyl group; and (v) tertiary hydrocarbyl amines having a maximum of 30 carbon atoms.

12. A method of improving the performance of an engine, the method comprising combusting in said engine a fuel composition comprising as an additive one or more quaternary ammonium compounds as claimed in claim 1.

13. A method according to claim 12 wherein the engine is a gasoline engine and the fuel is a gasoline fuel.

14. A method according to claim 12 wherein the engine is a diesel engine having a fuel injection system which comprises a high pressure fuel injection (HPFI) system with fuel pressures greater than 1350 bar.

15. A method according to claim 12 wherein improvement in performance is achieved by combating deposits in the engine.

16. A method according to claim 15 which combats internal diesel injector deposits.

17. A method according to claim 15 which combats external diesel injector deposits, including injector nozzle deposits and injector tip deposits.

18. A method according to claim 14 which combats fuel filter deposits.

19. A method according to claim 12 wherein the improvement in performance is a power gain compared to when combusting an unadditised base fuel and with clean injectors.

20-22. (canceled)

23. A method of preparing a fuel composition as claimed in claim 7, the method comprising adding the quaternary ammonium salt additive to the fuel after the fuel has left the distribution terminal.

Description

EXAMPLE 1

[0346] Additive A1 was prepared as follows:

[0347] 65 g of a polyisobutyl-substituted succinic acid having an average polyisobutene molecular weight of 1000 (PIB1000SAcid) was dissolved in 50 ml of toluene in a 250 ml Radley's reactor flask. Six equivalents of water were added followed by two equivalents of dimethylethanolamine and two equivalents of epoxybutane. The reaction was heated at 60° C. After 6 hours a further equivalent of epoxybutane was added. After a further 6 hours the volatiles were removed on a rotary evaporator and the product made up to a 50% w/w solution in Shellsol A150.

EXAMPLE 2

[0348] Additive A2 was prepared as follows:

[0349] 48 g of oleic acid was mixed with 50 ml of toluene in a 250 ml Radley's reactor flask. Six equivalents of water were added followed by one equivalent of dimethylethanolamine and epoxybutane. The reaction was heated at 60° C. After 6 hours a further equivalent of epoxybutane was added. After a further 6 hours the volatiles were removed on a rotary evaporator and the product made up to a 50% w/w solution in Shellsol A150.

EXAMPLE 3

[0350] Additive A3 was prepared as follows:

[0351] 41 g of dodecenyl succinic acid was dissolved in 50 ml of toluene in a 250 ml Radley's reactor flask. Six equivalents of water were added followed by two equivalents of dimethylbutylamine and two equivalents of epoxybutane. The reaction was heated at 60° C. After 6 hours a further equivalent of epoxybutane was added. After a further 6 hours the volatiles were removed on a rotary evaporator and the product made up to a 50% w/w solution in ShelIsol A150.

EXAMPLE 4

[0352] Additive A4 was prepared as follows:

[0353] 22 g of acetic acid was mixed with 50 ml of toluene in a 250 ml Radley's reactor flask. Six equivalents of water were added followed by one equivalent of dimethylethanolamine and one equivalent of epoxybutane. The reaction was heated at 60° C. After 6 hours a further equivalent of epoxybutane was added. After a further 6 hours the volatiles were removed on a rotary evaporator and the product made up to a 50% w/w solution in 2-ethylhexanol.

EXAMPLE 5

[0354] Additive A5 was prepared as follows:

[0355] With FTIR monitoring, a sample of technical grade oleic acid (Fisher, 15.31 g) was caused to mix with iso-propylglycidyl ether (6.36 g) by magnetic stirring before addition of water (3.90 g) and finally N,N-dimethyl ethanolamine (14.45 g). Amine addition was accompanied by a temperature rise from 21 to 30° C., controlled by raising up an oil bath at ambient temperature around the flask. After the initial exotherm had died down, the oil bath heater was turned on and set to provide 100° C. After three hours at an internal temperature of 94-95° C. the reaction was adjudged, by FTIR, to be complete. The reaction mass was transferred to a pear-shaped flask and stripped at the rotary evaporator at 100° C., 9 mBar. Mass balances were consistent with formation of the desired 2-hydroxy-N-(2-hydroxyethyl)-3-isopropoxy-N,N-dimethylpropan-1-aminium salt of oleic acid. A trace of ester was apparent in the IR spectra.

EXAMPLE 6

[0356] Diesel fuel compositions were prepared comprising the additives listed in Table 1, added to aliquots all drawn from a common batch of RF06 base fuel, and containing 1 ppm zinc (as zinc neodecanoate).

TABLE-US-00001 TABLE 1 Fuel (ppm Composition Additive active) 1 A1 50 2 A2 50 3 A3 50 4 A4 50

[0357] Table 2 below shows the specification for RF06 base fuel.

TABLE-US-00002 TABLE 2 Limits Property Units Min Max Method Cetane Number 52.0 54.0 EN ISO 5165 Density at 15° C. kg/m.sup.3 833 837 EN ISO 3675 Distillation 50% v/v Point ° C. 245 — 95% v/v Point ° C. 345 350 FBP ° C. — 370 Flash Point ° C. 55 — EN 22719 Cold Filter ° C. — −5 EN 116 Plugging Point Viscosity at 40° C. mm.sup.2/sec 2.3 3.3 EN ISO 3104 Polycyclic % m/m 3.0 6.0 IP 391 Aromatic Hydrocarbons Sulphur Content mg/kg — 10 ASTM D 5453 Copper Corrosion — 1 EN ISO 2160 Conradson Carbon % m/m — 0.2 EN ISO 10370 Residue on 10% Dist. Residue Ash Content % m/m — 0.01 EN ISO 6245 Water Content % m/m — 0.02 EN ISO 12937 Neutralisation mg — 0.02 ASTM D 974 (Strong Acid) KOH/g Number Oxidation Stability mg/mL — 0.025 EN ISO 12205 HFRR (WSD1,4) μm — 400 CEC F-06-A-96 Fatty Acid Methyl prohibited Ester

EXAMPLE 7

[0358] Fuel compositions 1 to 4 listed in table 1 were tested according to the CECF-98-08 DW 10 method.

[0359] The engine of the injector fouling test is the PSA DW10BTED4. In summary, the engine characteristics are:

[0360] Design: Four cylinders in line, overhead camshaft, turbocharged with EGR

[0361] Capacity: 1998 cm.sup.3

[0362] Combustion chamber: Four valves, bowl in piston, wall guided direct injection

[0363] Power: 100 kW at 4000 rpm

[0364] Torque: 320 Nm at 2000 rpm

[0365] Injection system: Common rail with piezo electronically controlled 6-hole injectors.

[0366] Max. pressure: 1600 bar (1.6×10.sup.8 Pa). Proprietary design by SIEMENS VDO

[0367] Emissions control: Conforms with Euro IV limit values when combined with exhaust gas post-treatment system (DPF)

[0368] This engine was chosen as a design representative of the modern European high-speed direct injection diesel engine capable of conforming to present and future European emissions requirements. The common rail injection system uses a highly efficient nozzle design with rounded inlet edges and conical spray holes for optimal hydraulic flow. This type of nozzle, when combined with high fuel pressure has allowed advances to be achieved in combustion efficiency, reduced noise and reduced fuel consumption, but are sensitive to influences that can disturb the fuel flow, such as deposit formation in the spray holes. The presence of these deposits causes a significant loss of engine power and increased raw emissions.

[0369] The test is run with a future injector design representative of anticipated Euro V injector technology.

[0370] It is considered necessary to establish a reliable baseline of injector condition before beginning fouling tests, so a sixteen hour running-in schedule for the test injectors is specified, using non-fouling reference fuel.

[0371] Full details of the CEC F-98-08 test method can be obtained from the CEC. The coking cycle is summarised below.

[0372] 1. A warm up cycle (12 minutes) according to the following regime:

TABLE-US-00003 Duration Engine Speed Torque Step (minutes) (rpm) (Nm) 1 2 idle <5 2 3 2000 50 3 4 3500 75 4 3 4000 100

[0373] 2. 8 hrs of engine operation consisting of 8 repeats of the following cycle

TABLE-US-00004 Duration Engine Speed Load Torque Boost Air After Step (minutes) (rpm) (%) (Nm) IC (° C.) 1 2 1750 (20) 62 45 2 7 3000 (60) 173 50 3 2 1750 (20) 62 45 4 7 3500 (80) 212 50 5 2 1750 (20) 62 45 6 10 4000 100 * 50 7 2 1250 (10) 20 43 8 7 3000 100 * 50 9 2 1250 (10) 20 43 10 10 2000 100 * 50 11 2 1250 (10) 20 43 12 7 4000 100 * 50 *for expected range see CEC method CEC-F-98-08

[0374] 3. Cool down to idle in 60 seconds and idle for 10 seconds

[0375] 4. 4 hrs soak period

[0376] The standard CEC F-98-08 test method consists of 32 hours engine operation corresponding to 4 repeats of steps 1-3 above, and 3 repeats of step 4. ie 56 hours total test time excluding warm ups and cool downs.

[0377] FIG. 1 shows the DW10 test results for compositions 1 and 3.

[0378] FIG. 2 shows the DW10 test results for compositions 2 and 4.

EXAMPLE 8

[0379] Due to the surprising apparent increase in power observed when using additives of the invention a further modified DW10 test was carried out.

[0380] An initial base fuel test at an independent laboratory, with the reference fuel RF-06 base fuel comprising 1 ppm zinc had shown a power-loss of 8.27% over the 32 hour test.

[0381] When, at the same facility, additive A2 was tested at a treat rate of 50 ppm active in the same fuel comprising 1 ppm zinc it showed a power-increase of 3.21%. The power increase appeared very soon after the start of test, with an increase of 2.1% recorded after one hour.

[0382] This amount of power increase in this test is surprising. Testing of the RF-06 reference fuel, without any zinc or additive, does not give any power-loss, but equally does not give any power increase, over the 32 hr test.

[0383] To verify the power-increase found with additive A2, another test was set up on a different DW10 engine at a second independent laboratory. This test was only run for 10 hours, but this was long enough to observe a power increase of 3.7%, and again the power increase was observed in the first few hours.

[0384] In a subsequent test, at the second laboratory, the CEC F-098-08 DW10 Engine Test was run on the base RF-06-03 reference fuel (i.e. with no Zn added) containing 50 ppm of additive A2 made according to Example 2. Power increased within the first hour before levelling off at a gain of 1.8%. After 16 hours the fuel was changed to unadditised RF-06 base fuel. A power difference between the two otherwise identical fuels was immediately obvious, with the second fuel, after 16 hours of operation, giving an increase of only 0.9% over the initial pre-test checks. Finally, the injectors were removed and cleaned (as normal between tests) and on return to the engine and over an 8 hour test the power output was indistinguishable from that of the previous 16 hours.

EXAMPLE 9

[0385] Additive A6 was prepared as a 50% w/w solution in 2-ethyl hexanol as follows:

[0386] 7.0 g of a polyisobutyl-substituted succinic acid having an average polyisobutene molecular weight of 1000 (PIB1000SAcid) was dissolved in 10.82 ml of 2-ethylhexan-1-ol in a boiling tube. Two equivalents of dimethylethanolamine and two equivalents of 1,2-epoxybutane were added and the reaction heated at 95° C. for 6 hours. Product was confirmed via FTIR spectra.

EXAMPLE 10

[0387] Further compounds of the invention were prepared using a method analogous to example 9 except that the acid was replaced by an equivalent amount of:

TABLE-US-00005 Additive Acid A7 Oleic Acid A8 Acetic Acid A9 Octadecenylsuccinic acid

EXAMPLE 11

[0388] Additive A10 was prepared using a method analogous to example 1 except that the acid was replaced by an equivalent amount of a mixture of dimerised fatty acids.

EXAMPLE 12

[0389] Further compounds of the invention were prepared using a method analogous to example 2 except that the acid was replaced by an equivalent amount of:

TABLE-US-00006 Additive Acid A11 Naphthenic acid A12 Benzoic acid A13 Salicylic acid A14 Mixture of dimerised fatty acids A15 Dodecenylsuccinic acid

EXAMPLE 13

[0390] Additive A20, Bis-(N,N,N-triethyl-N-methylammonium) octadecenyl succinate was prepared as follows:

[0391] Triethylamine (2.779 g, 27.2 mMol), dimethylcarbonate (9.507 g, 106 mMol) and methanol (12.5 cm.sup.3) were charged to a tube and heated, with stirring, for three hours at 130° C. under autogeneous pressure. The formation of a methyl carbonate salt was confirmed by FTIR (characteristic absorbance at 1651 cm.sup.−1).

[0392] Material from the tube was transferred to a round-bottom flask and reacted with a single equivalent (acid value basis, 0.5 molar equivalents) of octadecenyl succinic acid, as set out above. Significant levels of foaming were observed on stripping volatiles at the rotary evaporator. A product with the expected characteristic FTIR absorbances (1574 and cm.sup.−1) was obtained with good mass balance and taken up into solution in 50 wt % 2-ethylhexanol.

EXAMPLE 14

[0393] Additive A22, N,N,N-trimethyl-2-hydroxy ethylammonium oleate was prepared as follows

[0394] N,N-dimethyl ethanolamine (2.456 g, 27.6 mMol), dimethyl carbonate (9.95 g, 110 mMol) and methanol (12 cm.sup.3) were charged to a tube and heated to 130° C. for 75 minutes. The FTIR spectrum of the reaction mixture showed an absorbance at 1644 cm.sup.−1, characteristic of methyl carbonate salts. The reaction product was further reacted with oleic acid (7.844 g, 27.8 mMol), evolving gases over a few minutes while forming a clear solution. The absorbance ascribed to methyl carbonate was essentially entirely removed and replaced by clear features at 1575 and 1386 cm.sup.−1, characteristic of carboxylate salts. The reaction mixture was stripped at the rotary evaporator forming a brown viscous oil. The oil was dissolved in Shellsol A150 (50 wt %)

EXAMPLE 15

[0395] 105 ppm of each of the additive compounds listed in Table A was added to RF06 base fuel. Each of the fuel compositions prepared was tested using Jet Fuel Thermal Oxidation Test (JFTOT) equipment. In this test 800 ml of fuel is flowed over an aluminium tube heated to 260° C. at a pressure of approximately 540 psi (3.72×10.sup.6 Pa). The test duration is 2.5 hours. At the end of test the aluminium tube is removed and the thickness of deposit compared to the base fuel.

TABLE-US-00007 TABLE A Fuel Treat rate ppm w/w Deposit Thickness Composition Additive active (nm) 5 0 No additive 377 6 A1 105 49 7 A2 105 109 8 A4 105 57 9 A20 105 43 10 A22 105 130

[0396] These results show that additives of the present invention can lead to reduced deposits.

EXAMPLE 16

[0397] The effectiveness of the fuel compositions of the present invention in older engine was assessed using a standard industry test—CEC test method No. CEC F-23-A-01.

[0398] This test measures injector nozzle coking using a Peugeot XUD9 A/L Engine and provides a means of discriminating between fuels of different injector nozzle coking propensity. Nozzle coking is the result of carbon deposits forming between the injector needle and the needle seat. Deposition of the carbon deposit is due to exposure of the injector needle and seat to combustion gases, potentially causing undesirable variations in engine performance.

[0399] The Peugeot XUD9 A/L engine is a 4 cylinder indirect injection Diesel engine of 1.9 litre swept volume, obtained from Peugeot Citroen Motors specifically for the CEC PF023 method.

[0400] The test engine is fitted with cleaned injectors utilising unflatted injector needles. The airflow at various needle lift positions have been measured on a flow rig prior to test. The engine is operated for a period of 10 hours under cyclic conditions.

TABLE-US-00008 Stage Time (secs) Speed (rpm) Torque (Nm) 1 30 1200 ± 30 10 ± 2 2 60 3000 ± 30 50 ± 2 3 60 1300 ± 30 35 ± 2 4 120 1850 ± 30 50 ± 2

[0401] The propensity of the fuel to promote deposit formation on the fuel injectors is determined by measuring the injector nozzle airflow again at the end of test, and comparing these values to those before test. The results are expressed in terms of percentage airflow reduction at various needle lift positions for all nozzles. The average value of the airflow reduction at 0.1 mm needle lift of all four nozzles is deemed the level of injector coking for a given fuel.

[0402] A fuel additive formulation containing Additive A2 from Example 2 together with solvent, cetane number improver, corrosion inhibitor, demulsifier, antifoam and metal deactivator was added to diesel fuel at a treat rate to give an active treat rate of 58 ppm of Additive A2. A keep clean test was run using this fuel and the results are shown below.

TABLE-US-00009 XUD9 Keep Clean % Nozzle Treat Fouling Fuel Base rate ppm @0.1 mm Composition Fuel Additive w/w active needle lift RF-06 — n/a 73.0 11 RF-06 A2 58 11.0

[0403] A clean up test was run with the same formulation at twice the treat rate. In the clean up test, a test cycle is run on unadditised fuel (RF-06) to foul the injectors, followed by a run with additised fuel to determine the ability of the additive to clean the fouled injectors.

TABLE-US-00010 XUD9 Clean-Up % Nozzle Treat rate Fouling Fuel Base ppm w/w @ 0.1 mm Test Composition Fuel Additive active needle lift Phase % clean-up RF-06 — n/a 73.0 Dirty-Up 12 A2 116 2.0 Clean-Up 97.2

EXAMPLE 17

[0404] Similar fuel compositions to 11 and 12 (but with the addition of 1 ppm zinc as zinc neodecanoate) were also tested in the DW10 test described in example 7. Fuel composition 13 was run as a keep clean test. Fuel composition 14 was run as a clean up test. The results are given in FIGS. 3 and 4.

TABLE-US-00011 Fuel Treat rate ppm Composition Base Fuel Additive w/w active RF-06 + 1 ppm Zn — n/a 13 RF-06 + 1 ppm Zn A2  58 14 RF-06 + 1 ppm Zn A2 116

EXAMPLE 18

[0405] In Europe the Co-ordinating European Council for the development of performance tests for transportation fuels, lubricants and other fluids (the industry body known as CEC), has developed a new test for additives for modern diesel engines such as HSDI engines. The CEC F-110-xx.sup.1 test is used to assess whether diesel fuel is suitable for use in engines meeting new European Union emissions regulations known as the “Euro 5” regulations. The test is based on a Peugeot DW10 engine using Euro 5 injectors, and is commonly referred to as DW10C test. This test measures the effects of deposits on the injectors specific to IDID's with respect to injector sticking.

[0406] In this test thermocouples are positioned in the engine to enable the exhaust temperature of each cylinder to be measured. This, in conjunction with other measured parameters, allows injector sticking to be tested.

[0407] The engine of the injector fouling test is the PSA DW10CTED4/E5. In summary, the engine characteristics are:

[0408] Design: Four cylinders in line, overhead camshaft, turbocharged with EGR

[0409] Capacity: 1997 cm.sup.3

[0410] Combustion chamber: Four valves, bowl in piston, wall guided direct injection

[0411] Power: 120 kW at 3750 rpm

[0412] Torque: 340 Nm at 2000 rpm

[0413] Injection system: Common rail with piezo electronically controlled 6-hole injectors.

[0414] Max. pressure: 1600 bar (1.6×10.sup.8 Pa). Proprietary design by Delphi

[0415] Emissions control: Conforms with Euro V limit values when combined with exhaust gas post-treatment system (DPF)

[0416] This engine was chosen as a design representative of the modern European high-speed direct injection diesel engine capable of conforming to present and future European emissions requirements. The common rail injection system uses a highly efficient nozzle design with rounded inlet edges and conical spray holes for optimal hydraulic flow. This type of nozzle, when combined with high fuel pressure has allowed advances to be achieved in combustion efficiency, reduced noise and reduced fuel consumption, but are sensitive to influences that can cause injector sticking.

[0417] The test is run with current injector design conforming to Euro V injector technology.

[0418] Full details of the CEC F-110-xx test method can be obtained from the CEC. The test cycle is summarised below.

TABLE-US-00012 1. Warm-Up stages: Duration Engine Speed Torque Step (minutes) (rpm) (Nm) 1 2 1000 10 2 3 2000 50 3 4 3500 75 4 3 3750 100

TABLE-US-00013 2. Main Run Engine Duration Speed Torque Step (seconds) (rpm) (Nm) 1 1470 1750 280 1-Ramp .fwdarw. 2 270 3000 — 2-Ramp .fwdarw. 1 30 — —

[0419] The test procedure consists of alternating sequences of soak periods followed by cold starts preceding main run cycles of engine operation. There are 5 main runs and 6 cold starts. If the engine should fail to start or stall during engine operation and cannot be restarted the test is aborted.

[0420] During the test ECU parameters are recorded together with exhaust temperatures to evaluate any indication of injector sticking. These parameters contribute to an overall demerit rating at the conclusion of the test.

[0421] .sup.1Test procedure still in draft format and final CEC issue number not yet available.

[0422] The base fuel for the test was CEC base fuel DF79 containing 0.5 mg/kg Na in the form of Sodium Naphthenate and 10 mg/kg dodecyl succinic acid (DDSA).

[0423] The engine was run on base fuel according to the current procedure. Over the 30 hour test cycle, widening exhaust temperatures were observed after 18 hours, providing indication of injector sticking. At this point the engine was switched to the same base fuel (i.e. DF79+0.5 mg/kg Na+10 mg/kg DDSA)+120 mg/kg (active) A2. After 24 hours (i.e. 6 hours clean-up), the engine showed improved exhaust temperatures and this continued to 30 hours indicating normal engine operation and no evidence of injector sticking.