TAJENDRA GUPTA is Senior Vice President, Sales, Marketing & Technical, Total Oil India Pvt Ltd
Regulatory bodies and markets in contemporary times demand higher fuel efficiency, compliance to stricter emission norms as well as enhanced engine performance and durability. And to meet these demands, lubricant companies along with automobile manufacturers, are striving to protect our environment and provide a good customer experience. Delivering higher fuel economy targets requires unprecedented lubricant performance, lubricant robustness, increased cleanliness & durability, and greater fuel economy throughout the entire oil change interval.
WHAT IS ILSAC?
The International Lubricant Standardization and Approval Committee (ILSAC) works with the API (American Petroleum Institute) in developing performance standards for passenger car engine oil used in gasoline-fuelled engines. Top US & Japanese vehicle manufacturers follow ILSAC standards for passenger car engine oils. ILSAC GF-5 was introduced on October 1, 2010 (for 2011) that mainly targeted fuel economy, high temperature deposit protection, sludge protection, seal compatibility and protection of emission control systems. Nearly a decade later, ILSAC is ready with the new standards, GF-6. In July 2019, through the Engine Oil Licensing and Certification System (EOLCS), the API officially announced May 1, 2020 as the first license date of the new ILSAC GF-6 and API SP specifications.
WHY DO WE NEED NEW LUBRICANTS STANDARD?
Due to the global warming phenomenon, reduction of greenhouse gases is a huge concern for regulatory authorities, oil & gas companies and automobile manufacturers. To understand the need of new lubricants standard, we must know about two regulations by Indian authorities – (i) Corporate Average Fuel Economy (CAFÉ) and (ii) Bharat Stage emission regulations. The CAFÉ regulation mainly focusses on the reduction of COx (oxides of carbon) emission, whereas BS emission regulations focusses on overall emission including NOx, particulate matter (PM), hydrocarbons, etc.
According to the Bureau of Energy Efficiency (BEE), the average weight of cars in 2022 would be 1,145 kg and would require the average fuel consumption to be less than 4.77 l/100 km at this average weight. As of April 1 2020, the Indian government has decided to implement Bharat Stage 6 emission norms.
CAFE combined with BS 6 throws up a challenge for carmakers to drastically reduce emissions. In order to meet the fuel economy and emission norm challenges, the engine technology has evolved significantly, and requires high performing lubricants. Engine downsizing, gasoline direct injection, use of turbocharger, variable valve timing, start/stop technology, gasoline particulate filter, three-way catalytic convertor, etc. are some of the hardware changes introduced by automobile manufacturers. The new lubricants standard has been designed to further improve fuel economy and provide complete engine protection with new hard-ware. Key drivers for the development of GF-6 include the push for greater fuel economy and problems associated with turbocharged gasoline direct injection engines such as low-speed pre-ignition & timing chain wear.
WHAT IS LSPI (LOW-SPEED PRE-IGNITION)?
LSPI is a type of pre-ignition that occurs at low speed/ high torque in turbocharged gasoline direct injection engines. Engine downsizing with turbocharging increases the power density of engines. Such engines are prone to LSPI, which, in the mild cases create engine noise but in severe cases may lead to catastrophic engine failure. There are several theories on LSPI. In short, there are two main reasons – one, in gasoline direct injection (GDI) engines, atomised fuel mixes with oil and auto-ignites creating LSPI, and secondly, floating solid particles (deposits due to incomplete combustion) in the combustion chamber can act as high temperature spot leading to LSPI.
Most IC engines work on four strokes – intake stroke, compression stroke, ignition or power stroke, and exhaust stroke. In gasoline engines, power is generated by burning air-fuel mixture through a spark plug. In spark ignition (SI) engines, auto-ignition & pre-ignition are two major issues related to the combustion of air-fuel mixture. In case of auto-ignition, air-fuel mixture ignites itself creating a local flame front. This creates the problem of knocking and happens mostly with low octane fuels. A basic diagram (1) demonstrates this problem. Pre-ignition, as the name suggests, represents the combustion of air-fuel mixture triggered by a hot-spot rather than the electrical spark before the spark time.
FORMULATING RIGHT ENGINE OIL TO REDUCE LSPI
Engine oil plays an important role in reducing LSPI. Total, with its research partners, has conducted extensive research in this area. However, LSPI occurs randomly and it is difficult to make an exact correlation. It is found that certain detergency additive elements such as Calcium (Ca) or Sodium (Na) may cause LSPI, whereas Molybdenum (Mo) or Zin (Zn) may reduce LSPI.
WHAT ARE THE TESTS MENTIONED IN GF-6?
ILSAC GF-5 did not include (Society of Automotive Engineers) SAE 0W-16 grade, which would become more prevalent in the future engines. The older engines are not designed to operate on SAE 0W-16 engine oils. That is why ILSAC has decided to create two subcategories: ILSAC GF-6A & ILSAC GF-6B. ILSAC GF-6A will be backward compatible to ILSAC GF-5 specifications using SAE 0W-20, 0W-20, 5W-20, 5W-30 and 10W-30. ILSAC GF-6B will be limited to SAE 0W-16 engine oils.
ILSAC GF-6 specifications contains various engine tests (classified as sequence) and bench tests, including:
:: Ability of engine oil for piston cleanliness → Sequence III
:: Oxidation resistance of engine oil → Sequence III
:: Ability of engine oil to provide cam wear protection → Sequence IV
:: Protection of engine from sludge & varnish → Sequence V
:: Fuel economy properties of engine oil → Sequence VI
:: Protection against corrosion → Sequence VIII
:: Protection against low-speed pre-ignition (LSPI) → Sequence IX
:: Protection of timing chain wear → Sequence X
Apart from these some other bench tests are also part of GF-6 specifications, which includes catalyst compatibility (such as P content & S content), evaporation loss of engine oil, foaming tendency & stability, etc.
With respect to GF-5, GF-6 oils will have better oxidation stability, provide cleaner piston, better protection against sludge & varnish and higher fuel economy. Apart from that ultra-low viscosity (0W-16), protection against LSPI & timing chain wear protection are some added advantages of GF-6 engine oil, which were not there in GF-5.
Owing to the increasing strictness of emission norms, automobile manufacturers are designing engines that have higher power density. Such engines run hotter and need better protection. ILSAC GF-6 standard for engine oils will ensure full protection of the engine against wear, deposit, corrosion, sludge, and others, while providing extra mileage and noise-free running of vehicles. This will provide comfort and cost-savings to an end customer due to lesser fuel requirement.