ILSAC GF-6, API SP & dexos: Making Sense of Motor Oil Specifications

As engine-operating conditions grow more severe, so do the demands placed on your motor oil. Hence the need for updated oil specifications, like ILSAC GF-6, API SP and GM* dexos1 Gen 2, Gen 3 and dexos R.*

Engine technology like turbochargers, direct injection and variable valve timing (VVT) place increased stress on your engine oil. This, in turn, has led to the introduction of stricter motor oil specifications.

Here’s what we’re going to cover:

• • How do fuel-economy standards increase engine stress?
  • What is low-speed pre-ignition (LSPI)?

• • How does motor oil help prevent LSPI?
  • Wha are ILSAC GF-6, API SP and GM dexos?
  • Do AMSOIL synthetic motor oils meet the latest specs?

Improved fuel economy

Corporate Average Fuel Economy (CAFE) standards require a fleet-wide average of about 40 mpg by 2026 in the United States.

To meet these requirements the automotive industry has focused on smaller, more fuel-efficient engines. In fact, most new vehicles now feature gasoline direct-injection (GDI), a turbocharger or both (T-GDI).

Severe operating conditions

Smaller, more-efficient engines that make the power and torque of higher-displacement engines undergo more severe operating conditions that can lead to…

• Severe engine knock, also called low-speed pre-ignition (LSPI)
• Increased engine temperatures
• Compromised fuel injectors
• Increased wear and deposits if the oil isn’t adequate

“The biggest motor-oil-related challenge is LSPI, which can destroy pistons and connecting rods.”

LSPI can cause cracked pistons and rods

LSPI is the spontaneous ignition of the fuel/air mixture before spark-triggered ignition. It is a modern version of engine knock, which has been around since the first internal combustion engines.

However, LSPI occurs under low-speed, high-torque conditions, such as taking off from a stoplight in T-GDI engines. This scenario can create conditions where the fuel/air ignites too early in the combustion cycle, throwing off the engine’s timing. The expanding combustion charge collides with the piston as it’s moving up the cylinder, potentially destroying the pistons or connecting rods.

Oil can help prevent LSPI

Experts suggest the cause is due to oil/fuel droplets or deposits in the cylinder chamber that ignite while the piston is still traveling upward. The droplets and deposits contain enough heat to ignite the air/fuel mixture before spark-triggered ignition.

Research shows that oil formulation plays a role in reducing LSPI.

Certain motor oil ingredients can promote LSPI, while others can help reduce it. It’s tempting to consider boosting additives that help reduce LSPI in motor oil formulations, but some of those additives are intentionally reduced or left out of motor oil formulations for other reasons.

The scientific balancing act confronting oil engineers is not easy. Vehicles need motor oils that deliver excellent wear protection, resist the increased heat of modern turbocharged engines, prevent deposits and combat LSPI. But it’s the performance of the entire oil formulation that matters, not just one or two ingredients. AMSOIL Signature Series achieved 100% protection against LSPI when tested against GM’s dexos1 Gen 2 specification – see image below for details.

ILSAC GF-6, API SP and GM dexos

Next-generation motor oils need to pass an LSPI test to meet these new demands. General Motors was first out of the gate and required oils to pass its own LSPI test. Its GM dexos1 Gen 2 specification took effect Aug. 31, 2017. GM dexos1 Gen 3 specification arrived in 2021 to further address the challenges that smaller, higher-powered engines present.

In 2022, GM launched a new dexos R motor oil specification covering 0W-40 and 5W-50 motor oils that can withstand the rigors of high-speed and high-load conditions created during high-performance driving. Currently, the specification only applies to high-performance engines used in Corvettes* and Camaros.*

These advanced engines with high power density, forced induction, multi-point fuel injection, cylinder deactivation and emissions systems are driving demand for more advanced lubricants. Modern high-performance vehicles push engine technologies to another level, requiring a motor oil that can protect components operating continuously under extreme heat and high-load conditions.

AMSOIL Signature Series already outperforms the dexos R specification.

The latest American Petroleum Institute (API) specification – API SP – and the latest International Lubricants Standardization and Approval Committee (ILSAC) specification – GF-6 – essentially mirror one another.

ILSAC has set another precedent in the passenger-car motor oil market by splitting its specification into two parts. One of the main differences between the two specifications is compatibility. Both versions focus on wear protection, prevention of LSPI and improved engine cleanliness. However, GF-6B features a more stringent fuel economy test – see the chart below.

Engine oils can easily be identified as ILSAC GF-6A or 6B by the API emblem on the front label of the packaging. A shield represents the GF-6B specification, while the traditional starburst indicates a GF-6A product. However, both ILSAC specifications meet the industry-standard API SP specification, which is the most common recommendation in owners’ manuals.

AMSOIL meets the latest specs

AMSOIL synthetic motor oils meet or exceed the latest industry standards, including ILSAC GF-6, API SP, GM dexos1 Gen 2 and Gen 3, and dexos R. You can safely use our synthetic motor oils in engines that call for any of these specifications.

In fact, AMSOIL Signature Series outperforms GM’s dexos1 Gen 2 specification – see image below for details.

AMSOIL 10W-40 Synthetic Motor Oil became the first synthetic motor oil in the world to meet American Petroleum Institute service requirements in 1972. We’ve continued developing advanced lubricant formulations to provide our customers with the best protection and performance available for their machines.