Diesel engine builders have been developing new engines with advanced emissions controls to meet greatly tightened EPA emission requirements for engines due to go into effect in the year 2007. Effective with the 2007 model year, the U.S. Environmental Protection Agency set stringent limits on nitrogen oxide (NOx) and particulate matter (PM) emissions from on-highway trucks and buses. Engines incorporating diesel oxidation catalysts and particulate filters will require significantly revised lubricant formulations than in the past.
Consequently, engine manufacturers have been developing diesel engines that not only use diesel particulate filters that trap and further reduce soot emissions but also which operate on pollution-reducing ultra-low-sulfur diesel(ULSD) fuel and utilize cooled exhaust gas recirculation (EGR) devices to redirect some of the exhaust gases normally emitted by the vehicle back into the engine, creating more internal soot.
Because the new engines operate at lower combustion and higher coolant temperatures and do not burn off the soot and other particles, and because the after treatment devices are easily damaged, existing oils, even those meeting the CI-4 or CI-4 PLUS standard, do not provide the necessary protection to meet the new emission requirements for on-highway trucks and buses.
In particular, certain performance enhancing additives used in the past will cause problems in their currently used concentrations in the new generation of diesel engines which utilize relatively sophisticated exhaust filtration systems. For instance, ash and other metallic components of the traditional additives are incombustible, and thus would remain in the system and threaten to foul the sophisticated filters that will be on the new engines, increasing maintenance costs and adding to the emissions. Therefore, low sulfur-ash-phosphorus (“low SAP”) lubricant oils will be required in the industry which incorporate limits placed on certain additive components in the lubricant oil as follows: <1.0% ash, <0.12% phosphorous, and <0.4% sulfur.
The American Petroleum Institute (API) has promulgated a new lubricant category designated “CJ-4,” that is specifically engineered to aid the next generation of low-emission diesel engines in meeting the 2007 engine emission standards. In order to comply with the new API CJ-4 standard, lubricant formulators and manufacturers have been facing the challenge of developing new cleaner lubricant additives and components that can deliver the combination of performance and purity that the new engines and standards demand.
For off-road use diesel engine applications, other pre-existing API oil specifications will still apply as applicable. For example, oils in the API CI-4 category are formulated for use in high-speed, four-stroke cycle diesel engines and were designed to meet the EPA exhaust emission standards that came into force in October 2002. These oils have been compounded for use in all applications with diesel fuels ranging in sulfur content up to 0.05% by weight. CI-4 PLUS, adopted in 2004, represented an enhancement to the CI-4 category. Oils meeting the CI-4 PLUS designation are formulated to meet additional soot-control requirements of specific engines with cooled EGR.
In addition to meeting ever-tightening industry standards for oil performance and purity, the present investigators also have identified a coolant system leak problem that can occur in diesel engines, such as small leaks in seals of engine coolant systems used in EGR engines, which can threaten the performance and proper operation of lubrication system. These small coolant leaks can lead to contamination of the engine lubricating oil, viz., the crankcase oil, with coolant (i.e., typically ethylene glycol, propylene glycol and/or other (poly)alkylene glycol and the like). Coolants may also contain corrosion inhibitors, and other additive agents (including bittering agents, etc.) The presence of the coolant in the lubricant system has been observed by the present investigators to induce and/or promote plugging problems in the oil filter.
Many patents have taught the manufacture and use of dispersant VII materials in engine oil formulations. These patents include, for example, U.S. Pat. Nos. 6,107,257; 5,182,041; 5,188,745; 5,238,588, 4,8636,623; 5,075,383; 6,107,258; 5,556,923; and European patents EP 0922752; EP 0909805; EP 0491456; EP 0510892; EP 0338672EP 0396297; EP0549196; and EP 0417904, all of which are incorporated herein by reference in their entirety for their teaching. None of these patents are understood to recognize and address both CJ-4, CI-4 Plus and CI-4 compliance and coolant contamination issues for diesel engine lubricating compositions.
Therefore, the present investigators have identified a need for CJ-4, CI-4 Plus and CI-4 lubricant formulations that can further multi-task to minimize or prevent oil filter plugging in heavy-duty diesel engines, such as cooled EGR engines. As will become apparent from the descriptions that follow, the invention addresses this need as well as providing other advantages and benefits.