S
SkyPup
Guest
Harm free use of diesel additives
Extensive testing is necessary to demonstrate that use of new detergents and defoamers will not create troubles in the field.
The contribution made by motor vehicles to air pollution has led to progressively tighter emissions limits worldwide, and is under continuous scrutiny Vehicle makers have achieved reductions in noxious emissions and operating costs, as well as better performance for diesel engines, enhancing the environmental acceptability of this type of powerplant. Environmental pressures have also brought fuel quality into the debate. Mandatory changes in fuel quality are being implemented, and debate continues about further fuel specification changes.
At the same time, additive technology is enhancing the quality of automotive diesel fuel. For example, uses of detergents to maintain the performance of injector systems and defoamers to allow fast filling are now common. Middle distillate flow improvers (MDFI) were initiated more than 30 years ago to ensure safe operations at low ambient temperatures. The early 1980s saw the introduction of wax anti-settling additives and detergent-based packages, while in the 1990s additives have been used to prevent problems associated with low-sulfur fuels, which lack natural lubricity and are designed to comply with tighter emissions regulations.
The increasing use of diesel fuel additives indicates recognition of their contributions. In the mid to late 1980s, detergent packages were mostly used in Western Europe. Nowadays, their application is common in the Americas and the Asia-Pacific region. Lubricity additive, a relative newcomer, is now used in most countries where legislation mandates sulfur levels of 500 ppm or less in automotive diesel fuel. In 1992, the mandate began in Sweden; in 1998, the mandate extends to the United States, Canada, essentially all of western Europe, Japan, and Taiwan.
Harm testing of lubricity additives
Several chemicals have been used as diesel lubricity additives; all of them restored the lubricity level. However, the introduction of new chemicals and new applications must be properly monitored to ensure that no secondary problems are experienced.
Four types of additive technologies were tested. Additive A is an aliphatic ester derivative; Additives B, C, and D are different types of carboxylic acids.
Studies of in-line diesel pumps, fuel-filter plugging, high-temperature cylinder bore polishing, foam inhibitors, and the presence of water in the fuel were conducted to determine the effects of these additive technologies.
In-line diesel pumps
Background — Problems of in-line diesel injection pump sticking were reported in the past. The reason for the field failure was attributed to interaction between the lubricity additive and used crankcase lubricating oil. A crude test method was developed to correlate the extent of the problem with the chemical types used as diesel lubricity enhancers. This procedure did show some correlation with the field, but the precision was poor, as additives could produce passing or failing results using essentially the same treat rate and test conditions. Similar in-line pump sticking problems were reported in several countries in the past 10 years (e.g., Canada and South Africa). During the European introduction of low-sulfur diesel fuel (<500 ppm), several problems were reported that again pointed at the possibility that crankcase oil can react with fuel additives. The reaction material then led either to in-line pump sticking and loss of engine power, and/or shorter life of fuel filters due to severe plugging.
Additive A was tested at the 1000 ppm level and showed no evidence of wear or deposit of the plunger/barrel assembly of the in-line pump. This was in keeping with expectations, as Technology A has been used in the marketplace for more than four years without any reported in-line pump sticking problem.
Additive B was tested at treat rates of 100 and 1000 ppm. At both levels there were severe problems with in-line pumps. Deposits were present on most plungers and the barrels showed signs of scuffing and polishing wear. The severity was treat-rate-dependent, but even the typical market treat rate of Additive B was enough to damage the barrel plunger assembly within one oil drain interval.
The effect of Additive B on engine performance was quite clear. Focusing on the 10-times treat rate test, evidence of poor idle quality, increased HC emissions, and unstable exhaust temperature appeared after only 240 hours. After 48 hours the engine started without any problem, and HC levels and exhaust temperature were as expected. After 460 hours, the engine failed to start, and when substainable combustion was achieved all the parameters measured pointed to major problems: 1) engine speed is erratic for a given governor setting, 2) HC levels are erratic, and 3) exhaust temperature begins to increase after only five minutes.
It was not possible to determine whether the behavior of the engine was due to the inability of the plunger to rotate or because the deposit prevailed over the pump plunger return spring. However, the observations carried out during the test are entirely consistent with the scenarios suggested above: 1) increased levels of noxious emissions, 2) poor idle quality, 3) poor driveability, and 4) unstable exhaust temperature.
Testing was also carried out on Additive C with some surprising results. By the end of 460 hours, the engine began to behave erratically, particularly at cold start. The pump was then dismantled, with no trace of deposit to the naked eye; all barrel-plunger assemblies were free to move. This protocol was repeated, with the same results.
One can only speculate about what happened. A possible reason could be that the level of deposit with Additive C is very small, hence starting the engine would clear it from the barrel plunger area, leading to assemblies free to move when the pump was evaluated. Another potential cause could be the formation of deposits in other parts of the fueling system (e.g., injectors).
The protocol presented here can discriminate between chemistries and rank them in an order similar to field experience. Its use will provide a tool able to validate new chemistries and thus ensure trouble-free application in the marketplace.
Fuel filter plugging problem
Fuel filter plugging has been a major issue since low-sulfur diesel fuel was introduced in Europe. Analysis of the filters shows that the interaction products between fuel and crankcase lubricant are the main components of the deposit responsible for plugging the fuel filter. Other fuel and diesel performance package components are present, but the main part of the deposit is lubricant-derived.
No specific project has been carried out, as the phenomenon is clearly similar to that experienced in the in-line pump. Both problems occur in the marketplace, mostly at the same time, and as the cause seems to be the same it is believed that solving the in-line pump deposit problem would cure the fuel filter issue. Additive A has specifically been introduced in markets where both phenomena have occurred. Its use has been reported not to give rise to any field-related problem associated with lube oil — diesel fuel — lubricity additive compatibility. This field result supports the use of the in-line pump test protocol to predict lube-oil/fuel compatibility issues in the fueling system of a diesel engine.
High-temperature cylinder bore polish
Background — The reported incidence of rapid increase in oil consumption related to rising levels of bore polish, together with the adoption of extended oil change intervals, prompted the industry to establish project groups with the purpose of developing a bench engine test method to evaluate lubricant performance in this area. The need for an engine test was paramount, as bore polishing problems take a long time to develop. Field trials to reproduce this phenomenon can take a long time and involve considerable mileage before any type of cylinder wear is experienced.
Diesel fuel, unlike gasoline, is injected when the piston is quite close to the top dead center, directly into the combustion chamber. The available liner surface at that point is quite limited, so adsorption of any chemical from the fuel matrix that is compatible with lubricating oil could lead to a high localized concentration increase. This is the area of the liner usually displaying the highest level of bore polish. Chemistries used as lubricity additives combine most of the following characteristics: 1) good thermal stability, 2) excellent friction modification capabilities, 3) ability to survive in the combustion chamber as a liquid, 4) an oleophillic part strong enough to ensure fuel and lube compatibility, 5) and a polar head that will tend to increase the rate of adsorption onto most metallic surfaces.
For example, Additive A has a closed-cup flash point above 200 C (392 F). This indicates that lubricity additive chemistries have the ability to survive in the combustion chamber for a long time. Therefore, there is a high probability for them to adsorb on the liner surface, where, due to their oleophillic characteristics, they are readily dissolved in oil. Then the polarity within the molecule drives them to the liner surface. Clearly all this is speculative, but the boundary conditions of the system described make it highly likely that this could happen in the combustion chamber. Fuel additives are currently added to gasoline to achieve fuel economy benefits. Again this supports the ÒadsorptionÓ theory.
The lubricity additive treat rate in fuel is usually quite low — 50-200 ppm in most cases. Even at such low levels the amount of fuel additive used per oil drain interval period far exceeds the oilÕs friction modifier concentration.
Not all of the lubricity additive is adsorbed onto the liner; a large part is burned during the combustion process. However, even if a small amount is adsorbed, the localized concentration increase can be dramatic due to the small amount of oil on the liner.
The additives were added into RL 133 oil at concentrations of one and ten mass percent, and the standard bore polish rig test was then carried out. At bulk fuel additive concentration of 1% in oil, there is a beneficial effect for Additive Technology A; the other two were neutral. At additive concentrations of 10% there is a clearly different grouping for the various additive types: Additive A is still beneficial; C and D are reducing surface roughness (DeltaRA).
Technology D was also tested after complete esterification. The resulting product has a performance similar to Technology A at 1 and 10% concentration in oil. These data seem to indicate that acid-based components, though of different chemical structure, have the ability to interact with the liner surface, leading to reduced surface roughness, in the bore polish screener test. Fuel-soluble ester derivatives adsorb on the liner surface, but they provide a positive contribution reducing the typical wear level of the reference oil used.
It must be considered that in the engine load/speed map there are a variety of conditions under which fuel additive adsorption is likely to be increased due to the unfavorable air/fuel ratio: high-speed conditions, any type of high-torque operations, transient conditions. Driving patterns encompassing a mix of those conditions are more likely to result in a higher level of fuel-additive-related bore polish.
Additives effects on foam inhibitor performance
Silicone derivatives are used as foam inhibitors in a broad range of industrial applications. Certain chemical agents are well known to impair the stability of foam, and for automotive diesel fuel the typical components used are polysiloxane/copolymers and terpolymers. Such components are usually insoluble materials, and their ability to inhibit foam arises from their ability to spread spontaneously over the surface of the foaming medium. Another essential condition for efficient foam suppression requires the inhibitor to have a relatively low surface tension — too low to be wetted by the foamy liquid. Then when the de-foaming agent approaches the vicinity of the surface, the medium allows the inhibitor to surface and then spread. Both mechanisms can be affected if the structure of the polysiloxane copolymer is changed by reaction or association with other chemicals.
To assess this type of interaction, additive technologies A and B were mixed with a proprietary polysiloxane copolymer known to reduce foam in automotive diesel applications. The test used is the ÒBNPÓ foam protocol in which both foam height and foam collapse time are measured. The results obtained point clearly to potential interactions between these components.
Additive Technology A has no affect on the performance of the diesel defoamer, while Technology B severely degrades the foam inhibition of the polysiloxane defoamer derivative. The effect is particularly marked for foam height, the parameter that is first experienced by the consumer when filling at service stations. The delivery nozzle would cut off at an earlier stage when Additive B is used.
Effect of additives with water
During the distribution process, there are several possibilities for water to come in contact with automotive diesel fuel. Diesel fuel reactivity with water is quite low, and no fuel additive should exacerbate it. The study aimed at assessing the effect that fuel additives have when water is present focused mainly in two areas: storage corrosion and reactivity with water.
Additive B is known to help prevent ferrous corrosion when used at 5-20 ppm in fuel. This effect is somewhat at odds with the requirement that this material be stored in stainless steel containers. The former implies protection, the latter implies chemical reactivity.
A variety of experiments were carried out to understand the mechanism involved. When Additive B was in contact with mild steel coupons its behavior was neutral until water was added. At that point Additive B starts to dissolve iron, and this can be measured; levels of iron after overnight soaking were at 70 ppm, and there was evidence of white sludge in bottom water. Thus there is evidence that Additive B dissolves iron in the presence of water. This phenomenon might not be detected just by looking at the surface of the storage container. Our mild steel coupon was ÒperfectÓ after the soaking period, suggesting that the whole surface is affected by the chemical attack.
Anticorrosion testing in diesel fuel shows Additive B to be an effective additive in this area at the standard treat rate. Increasing the concentration shows that Additive B can dramatically increase corrosion, particularly when ÒbasicÓ or sea water is used. These effects confirm again that in critical conditions Additive B can become a very effective corrosive chemical. Additive A, even at high concentrations, is neutral to mildly positive toward rust prevention.
Diesel fuel specifications in several parts of the world call for this grade to be essentially free of any haze at the point of sale. Testing aimed at assessing this phenomenon also included measuring light transmittance to assess the effect of additive addition on this parameter. Testing was conducted to assess Additives A and B with regard to their reactivity with water. Emulsion-forming tendencies, and particularly the interface rating and degree of separation between the fuel and water layer, are poor for Additive B when basic water is present. This supports the findings from our ÒcorrosionÓ experiment. This is in line with the ability that such a component has to generate salts in presence of water with a basic pH. Additive B also has a very poor performance in this area. There is no light transmittance after five minutes of the test, and even after one hour the level of haze is poor, with a pH 9.2 water.
Summary
Four additive technologies that have the ability to provide lubricity benefits in low-sulfur diesel fuel were tested to assess whether their use would result in any field-related problems. The protocol used involved standard test methods and two new procedures. The two new procedures are aimed at assessing: the ability to generate in-line pump deposits in a fired heavy-duty engine and the effect of additive technology on piston bore polish.
The performances of different additive technologies were quite different, confirming that extensive testing is required to ensure harm free performance in the field.
This information was supplied by R. Caprotti, Exxon Chemical Ltd.
Extensive testing is necessary to demonstrate that use of new detergents and defoamers will not create troubles in the field.
The contribution made by motor vehicles to air pollution has led to progressively tighter emissions limits worldwide, and is under continuous scrutiny Vehicle makers have achieved reductions in noxious emissions and operating costs, as well as better performance for diesel engines, enhancing the environmental acceptability of this type of powerplant. Environmental pressures have also brought fuel quality into the debate. Mandatory changes in fuel quality are being implemented, and debate continues about further fuel specification changes.
At the same time, additive technology is enhancing the quality of automotive diesel fuel. For example, uses of detergents to maintain the performance of injector systems and defoamers to allow fast filling are now common. Middle distillate flow improvers (MDFI) were initiated more than 30 years ago to ensure safe operations at low ambient temperatures. The early 1980s saw the introduction of wax anti-settling additives and detergent-based packages, while in the 1990s additives have been used to prevent problems associated with low-sulfur fuels, which lack natural lubricity and are designed to comply with tighter emissions regulations.
The increasing use of diesel fuel additives indicates recognition of their contributions. In the mid to late 1980s, detergent packages were mostly used in Western Europe. Nowadays, their application is common in the Americas and the Asia-Pacific region. Lubricity additive, a relative newcomer, is now used in most countries where legislation mandates sulfur levels of 500 ppm or less in automotive diesel fuel. In 1992, the mandate began in Sweden; in 1998, the mandate extends to the United States, Canada, essentially all of western Europe, Japan, and Taiwan.
Harm testing of lubricity additives
Several chemicals have been used as diesel lubricity additives; all of them restored the lubricity level. However, the introduction of new chemicals and new applications must be properly monitored to ensure that no secondary problems are experienced.
Four types of additive technologies were tested. Additive A is an aliphatic ester derivative; Additives B, C, and D are different types of carboxylic acids.
Studies of in-line diesel pumps, fuel-filter plugging, high-temperature cylinder bore polishing, foam inhibitors, and the presence of water in the fuel were conducted to determine the effects of these additive technologies.
In-line diesel pumps
Background — Problems of in-line diesel injection pump sticking were reported in the past. The reason for the field failure was attributed to interaction between the lubricity additive and used crankcase lubricating oil. A crude test method was developed to correlate the extent of the problem with the chemical types used as diesel lubricity enhancers. This procedure did show some correlation with the field, but the precision was poor, as additives could produce passing or failing results using essentially the same treat rate and test conditions. Similar in-line pump sticking problems were reported in several countries in the past 10 years (e.g., Canada and South Africa). During the European introduction of low-sulfur diesel fuel (<500 ppm), several problems were reported that again pointed at the possibility that crankcase oil can react with fuel additives. The reaction material then led either to in-line pump sticking and loss of engine power, and/or shorter life of fuel filters due to severe plugging.
Additive A was tested at the 1000 ppm level and showed no evidence of wear or deposit of the plunger/barrel assembly of the in-line pump. This was in keeping with expectations, as Technology A has been used in the marketplace for more than four years without any reported in-line pump sticking problem.
Additive B was tested at treat rates of 100 and 1000 ppm. At both levels there were severe problems with in-line pumps. Deposits were present on most plungers and the barrels showed signs of scuffing and polishing wear. The severity was treat-rate-dependent, but even the typical market treat rate of Additive B was enough to damage the barrel plunger assembly within one oil drain interval.
The effect of Additive B on engine performance was quite clear. Focusing on the 10-times treat rate test, evidence of poor idle quality, increased HC emissions, and unstable exhaust temperature appeared after only 240 hours. After 48 hours the engine started without any problem, and HC levels and exhaust temperature were as expected. After 460 hours, the engine failed to start, and when substainable combustion was achieved all the parameters measured pointed to major problems: 1) engine speed is erratic for a given governor setting, 2) HC levels are erratic, and 3) exhaust temperature begins to increase after only five minutes.
It was not possible to determine whether the behavior of the engine was due to the inability of the plunger to rotate or because the deposit prevailed over the pump plunger return spring. However, the observations carried out during the test are entirely consistent with the scenarios suggested above: 1) increased levels of noxious emissions, 2) poor idle quality, 3) poor driveability, and 4) unstable exhaust temperature.
Testing was also carried out on Additive C with some surprising results. By the end of 460 hours, the engine began to behave erratically, particularly at cold start. The pump was then dismantled, with no trace of deposit to the naked eye; all barrel-plunger assemblies were free to move. This protocol was repeated, with the same results.
One can only speculate about what happened. A possible reason could be that the level of deposit with Additive C is very small, hence starting the engine would clear it from the barrel plunger area, leading to assemblies free to move when the pump was evaluated. Another potential cause could be the formation of deposits in other parts of the fueling system (e.g., injectors).
The protocol presented here can discriminate between chemistries and rank them in an order similar to field experience. Its use will provide a tool able to validate new chemistries and thus ensure trouble-free application in the marketplace.
Fuel filter plugging problem
Fuel filter plugging has been a major issue since low-sulfur diesel fuel was introduced in Europe. Analysis of the filters shows that the interaction products between fuel and crankcase lubricant are the main components of the deposit responsible for plugging the fuel filter. Other fuel and diesel performance package components are present, but the main part of the deposit is lubricant-derived.
No specific project has been carried out, as the phenomenon is clearly similar to that experienced in the in-line pump. Both problems occur in the marketplace, mostly at the same time, and as the cause seems to be the same it is believed that solving the in-line pump deposit problem would cure the fuel filter issue. Additive A has specifically been introduced in markets where both phenomena have occurred. Its use has been reported not to give rise to any field-related problem associated with lube oil — diesel fuel — lubricity additive compatibility. This field result supports the use of the in-line pump test protocol to predict lube-oil/fuel compatibility issues in the fueling system of a diesel engine.
High-temperature cylinder bore polish
Background — The reported incidence of rapid increase in oil consumption related to rising levels of bore polish, together with the adoption of extended oil change intervals, prompted the industry to establish project groups with the purpose of developing a bench engine test method to evaluate lubricant performance in this area. The need for an engine test was paramount, as bore polishing problems take a long time to develop. Field trials to reproduce this phenomenon can take a long time and involve considerable mileage before any type of cylinder wear is experienced.
Diesel fuel, unlike gasoline, is injected when the piston is quite close to the top dead center, directly into the combustion chamber. The available liner surface at that point is quite limited, so adsorption of any chemical from the fuel matrix that is compatible with lubricating oil could lead to a high localized concentration increase. This is the area of the liner usually displaying the highest level of bore polish. Chemistries used as lubricity additives combine most of the following characteristics: 1) good thermal stability, 2) excellent friction modification capabilities, 3) ability to survive in the combustion chamber as a liquid, 4) an oleophillic part strong enough to ensure fuel and lube compatibility, 5) and a polar head that will tend to increase the rate of adsorption onto most metallic surfaces.
For example, Additive A has a closed-cup flash point above 200 C (392 F). This indicates that lubricity additive chemistries have the ability to survive in the combustion chamber for a long time. Therefore, there is a high probability for them to adsorb on the liner surface, where, due to their oleophillic characteristics, they are readily dissolved in oil. Then the polarity within the molecule drives them to the liner surface. Clearly all this is speculative, but the boundary conditions of the system described make it highly likely that this could happen in the combustion chamber. Fuel additives are currently added to gasoline to achieve fuel economy benefits. Again this supports the ÒadsorptionÓ theory.
The lubricity additive treat rate in fuel is usually quite low — 50-200 ppm in most cases. Even at such low levels the amount of fuel additive used per oil drain interval period far exceeds the oilÕs friction modifier concentration.
Not all of the lubricity additive is adsorbed onto the liner; a large part is burned during the combustion process. However, even if a small amount is adsorbed, the localized concentration increase can be dramatic due to the small amount of oil on the liner.
The additives were added into RL 133 oil at concentrations of one and ten mass percent, and the standard bore polish rig test was then carried out. At bulk fuel additive concentration of 1% in oil, there is a beneficial effect for Additive Technology A; the other two were neutral. At additive concentrations of 10% there is a clearly different grouping for the various additive types: Additive A is still beneficial; C and D are reducing surface roughness (DeltaRA).
Technology D was also tested after complete esterification. The resulting product has a performance similar to Technology A at 1 and 10% concentration in oil. These data seem to indicate that acid-based components, though of different chemical structure, have the ability to interact with the liner surface, leading to reduced surface roughness, in the bore polish screener test. Fuel-soluble ester derivatives adsorb on the liner surface, but they provide a positive contribution reducing the typical wear level of the reference oil used.
It must be considered that in the engine load/speed map there are a variety of conditions under which fuel additive adsorption is likely to be increased due to the unfavorable air/fuel ratio: high-speed conditions, any type of high-torque operations, transient conditions. Driving patterns encompassing a mix of those conditions are more likely to result in a higher level of fuel-additive-related bore polish.
Additives effects on foam inhibitor performance
Silicone derivatives are used as foam inhibitors in a broad range of industrial applications. Certain chemical agents are well known to impair the stability of foam, and for automotive diesel fuel the typical components used are polysiloxane/copolymers and terpolymers. Such components are usually insoluble materials, and their ability to inhibit foam arises from their ability to spread spontaneously over the surface of the foaming medium. Another essential condition for efficient foam suppression requires the inhibitor to have a relatively low surface tension — too low to be wetted by the foamy liquid. Then when the de-foaming agent approaches the vicinity of the surface, the medium allows the inhibitor to surface and then spread. Both mechanisms can be affected if the structure of the polysiloxane copolymer is changed by reaction or association with other chemicals.
To assess this type of interaction, additive technologies A and B were mixed with a proprietary polysiloxane copolymer known to reduce foam in automotive diesel applications. The test used is the ÒBNPÓ foam protocol in which both foam height and foam collapse time are measured. The results obtained point clearly to potential interactions between these components.
Additive Technology A has no affect on the performance of the diesel defoamer, while Technology B severely degrades the foam inhibition of the polysiloxane defoamer derivative. The effect is particularly marked for foam height, the parameter that is first experienced by the consumer when filling at service stations. The delivery nozzle would cut off at an earlier stage when Additive B is used.
Effect of additives with water
During the distribution process, there are several possibilities for water to come in contact with automotive diesel fuel. Diesel fuel reactivity with water is quite low, and no fuel additive should exacerbate it. The study aimed at assessing the effect that fuel additives have when water is present focused mainly in two areas: storage corrosion and reactivity with water.
Additive B is known to help prevent ferrous corrosion when used at 5-20 ppm in fuel. This effect is somewhat at odds with the requirement that this material be stored in stainless steel containers. The former implies protection, the latter implies chemical reactivity.
A variety of experiments were carried out to understand the mechanism involved. When Additive B was in contact with mild steel coupons its behavior was neutral until water was added. At that point Additive B starts to dissolve iron, and this can be measured; levels of iron after overnight soaking were at 70 ppm, and there was evidence of white sludge in bottom water. Thus there is evidence that Additive B dissolves iron in the presence of water. This phenomenon might not be detected just by looking at the surface of the storage container. Our mild steel coupon was ÒperfectÓ after the soaking period, suggesting that the whole surface is affected by the chemical attack.
Anticorrosion testing in diesel fuel shows Additive B to be an effective additive in this area at the standard treat rate. Increasing the concentration shows that Additive B can dramatically increase corrosion, particularly when ÒbasicÓ or sea water is used. These effects confirm again that in critical conditions Additive B can become a very effective corrosive chemical. Additive A, even at high concentrations, is neutral to mildly positive toward rust prevention.
Diesel fuel specifications in several parts of the world call for this grade to be essentially free of any haze at the point of sale. Testing aimed at assessing this phenomenon also included measuring light transmittance to assess the effect of additive addition on this parameter. Testing was conducted to assess Additives A and B with regard to their reactivity with water. Emulsion-forming tendencies, and particularly the interface rating and degree of separation between the fuel and water layer, are poor for Additive B when basic water is present. This supports the findings from our ÒcorrosionÓ experiment. This is in line with the ability that such a component has to generate salts in presence of water with a basic pH. Additive B also has a very poor performance in this area. There is no light transmittance after five minutes of the test, and even after one hour the level of haze is poor, with a pH 9.2 water.
Summary
Four additive technologies that have the ability to provide lubricity benefits in low-sulfur diesel fuel were tested to assess whether their use would result in any field-related problems. The protocol used involved standard test methods and two new procedures. The two new procedures are aimed at assessing: the ability to generate in-line pump deposits in a fired heavy-duty engine and the effect of additive technology on piston bore polish.
The performances of different additive technologies were quite different, confirming that extensive testing is required to ensure harm free performance in the field.
This information was supplied by R. Caprotti, Exxon Chemical Ltd.
