The Highly Specific Life Of LS- And LT-Based Motor Oils

Ever since oil was first deemed usable for internal combustion consumption, it has been on an ever-changing path of improvements and specificity. Ironically, evolution is as much a part of your oil’s survival as it was of the animals that helped formulate it eons ago. The difference being, oil seems to take on a more revolutionary speed, rather than the snail’s pace of evolution. The dinosaurs didn’t have it so good.

Just a few short years ago, one of the major changes to our engine’s beloved lifeblood was the switch to synthetic oils, where the base stock of the oil was completely man-made, instead of refined from organic substances. This opened the door for higher-performing oils with characteristics more favorable to today’s engines. Of course, some specific refinements were necessary to preserve previous engine designs, such as flat-tappet camshafts with non-roller lifters. They need additional lubrication, especially at start-up, to prevent premature wear. In this case, oil’s evolution in specificity was to address a preexisting condition, necessary for earlier technology.

The first salvo of specificity was thrown when camshafts began shedding lobes due to a lack of zinc during break-in. Many break-in specific oils were created to help your flat-tappet engine get off to a good start.

As EPA standards and fuel mileage ratings became more restrictive, our super-slippery substance was found inadequate in other ways. Tolerances between moving parts decreased and piston rings began relying more on gas pressure and less on ring tension to keep them sealed against the cylinder wall. Other considerations such as Active Fuel Management (AFM), also known as Displacement On Demand (DoD), meant that our oil now needed to adjust its hydraulic tendencies to the ever-changing needs of our throttle position.

Beyond The Numbers

Whereas the good-ol’ days consisted of a syrupy supply of 20w-50 oils to keep parts from rubbing together excessively, current manufacturer-recommended oils for today’s late-model engines are routinely rated at 0w-20. The thinner-weight oils allow for less friction within the engine, which directly correlates into better fuel mileage. While the main reason for the difference in viscosity is due to internal tolerances and fuel mileage concerns, not all oil formulas are a factor of friction.

There's been a lot of talk lately about flat-tappet cams and "zinc". Actually, zinc when speaking of engines is is a family of additives called Zinc DiakylDithioPhosphates – better known as ZDDP. A little known fact is that ZDDP is not a lubricant until the ZDDP reacts under heat and load to create a phosphate glass film that protects the metal surface. On the down side, detergents and dispersant-additives in motor oil can actually compete against the zinc in your engine. That is why specific "break-in" oils are necessary for flat-tappet performance applications.

We spoke with Lake Speed, Jr., General Manager and Certified Lubrication Specialist at Driven Racing Oil about how oils have evolved to not only provide superior lubrication and excellent fuel economy, but also work with today’s technologies to provide long-lasting protection under various operating conditions.

Many folks perceive the change to synthetic oil as the final chapter in oil’s evolutionary tale, but with today’s direct-injection engines, even the all-encompassing synthetic oils were found to be wanting. The need for change comes from the new, direct-injection (DI) design and how it introduces the fuel into the combustion chamber.

Technologies, such as Variable Valve Timing (VVT) and Active Fuel Management (AFM) have pushed oils to rely more on their hydraulic properties as much as their lubricating abilities. That is why Driven has designed its LS-series of oils for engines which utilize these capabilities.

Simply put, Direct-injection is a more finely controlled supply of fuel into your car’s combustion chamber. Carbureted, throttle body injection, and even port-injected fuel systems introduce the fuel into the airflow long before it enters the combustion chamber. Port-injected systems have adjusted the injection-event to occur during the highest airflow within the intake port to give the most turbulence and help in vaporization of the fuel charge. Even so, the air/fuel mixture spends considerable degrees of crankshaft rotation inside the hot engine. This dwell time inside the intake tract, gives the fuel ample time to transfer into a burnable vapor.

A typical direct-injection engine has less than 160 degrees of crankshaft rotation to atomize the fuel compared to over 320 degrees of crankshaft rotation in a traditional port-injection or carbureted engine. When you decrease an engine’s speed, it also decreases the vapor-enhancing turbulence of the airflow. The combination of low speed and short dwell time for vaporization contributes to atomized (but not vaporized) raw fuel molecules existing in the combustion chamber before ignition.

The Low-Speed Problem

The presence of the raw fuel can create what is known as Low Speed Pre-Ignition (LSPI). During prolonged idle, fuel can accumulate around the piston rings and the upper ring lands. The fuel can inter-mix with the engine oil designed to lubricate the cylinder wall. At this point, the chemical side of LSPI becomes apparent. Intermixing fuel and oil could be a big problem, whether in the latest direct-injected engine or a vintage big-block. Now, today’s refinements in both fuel control and oil requirements takes the effects of intermingling them to a molecular level.

One of the added agents to motor oils are detergents to help keep the inside of the engine clean. Two of the most common types of engine detergents used in the industry are either Calcium- or Sodium-based. Calcium-based detergents are the most cost-effective detergents, and are widely used in off-the-shelf motor oils, typically in high concentrations.

The issue begins when the components used in the oil’s detergent additive chemically mixes with the fuel. The result is a blend of fuel and oil, which has a lower octane level than the fuel. Coupled with the typically, higher-compression ratios found in direct-injected engines (11.5:1 in LT1 engines and 10:1 in the supercharged LT4), it’s like running VERY bad fuel in all the wrong places.

Direct injection added another requirement to our engine's oil, due to it injecting the fuel directly into the combustion chamber. Decreasing Calcium detergents is meant to eliminate LSPI, conversely, DI-specific fuels require additional detergents to counter the engine's inherent dirtier operation.

The raw fuel doesn’t have sufficient time to fully vaporize, due to a lack of turbulence and an abbreviated dwell time. This fuel can puddle between the upper piston ring and ring land. When mixed with the oil, it can produce this low octane compound. When the throttle pedal is punched after extended idling, this compound can pre-ignite, causing severe damage to the piston rings and lands.

Getting Rid Of LSPI

To counter this potentially-destructive effect, Driven Racing Oil has created direct-injection-specific oils which eliminate Sodium detergents and greatly reduce Calcium detergents in an attempt to prevent LSPI. Its efforts were proven when a European racing series changed from European road-spec oil containing over 2,500 parts per million (ppm) of Calcium detergent to Driven’s XP9 racing oil, which contained only 250 ppm of Calcium detergent. The change to an oil with a lower-Calcium detergent level eliminated the LSPI-related engine failures.

LSPI is a result of non-vaporized fuel residing around the ring and lands of a piston. Severe damage can result!

Another factor contributing to LSPI is a fuel’s distillation curve, which displays how easily a fuel evaporates. Interestingly, whereas a racing or premium fuel is typically desired for performance driving, a standard fuel will vaporize more easily. While it is still necessary to have a high-enough octane to support an engine’s compression and performance needs, some racing fuels with a high distillation temperature can be detrimental in direct-injected engines. This is due to the higher octane racing fuel’s resistance to vaporization and the resulting LSPI occurring in direct-injected engines.

Why Are LS And LT Oils Different?

We asked Lake Speed Jr. about the differences between the two engines and why they have different oil needs. “The fuel delivery [port injection versus direct injection] and oiling system [manual pressure-relief valve versus ECU-controlled solenoid] make LS engines and LT engines very different in terms of oil needs. Displacement on Demand requires the oil to be a dedicated hydraulic fluid as well as a motor oil, so the oil needs to be formulated to do both. We incorporate that thinking into our products for these engines.”

Our DI-spec oils go beyond the dexos 1:Gen 2 certification to add protection for tuned and modified DI engines. – Lake Speed Jr., Driven Racing Oils

He addresses the difference between the two engines’ detergent requirements by saying, “Our LS oils use 2,000 ppm of Calcium and the DI oils use 1,500 ppm. Below 1,800 ppm, there are no issues with LSPI. We have two special additives in the DI oils to control the additional soot inherent with direct-injection. If it doesn’t say anything about being formulated for DI engines, then don’t use it in a DI engine.”

The change to direct-injection has brought another evolutionary change in engine oil. Driven Racing Oil's LS-series of oils are specifically designed to be used in LSx engines. Driven's DI-specific oils take it one step further and reduce the amount of Calcium as a detergent to eliminate LSPI.

General Motors has recently updated its oil ratings to better suit the new oiling needs of direct-injected engines. The previous dexos 1 specification addressed issues common to all gasoline engines, while the new dexos 1:Gen 2 incorporates testing to address LSPI and soot-related wear in direct-injected engines.

We asked Lake about the difference between Driven Racing Oil’s DI lubricants and GM’s dexos 1:Gen 2 rated oils. He replied, “The dexos 1:Gen 2 certification process incorporates testing to address LSPI and soot-related wear in stock engines. Our DI-spec oils go beyond the dexos 1:Gen 2 certification to add protection for tuned and modified DI engines.”

The Bottom Line

In the end, we’re benefactors of all the technology found in our late-model engines. We’re pushing power levels into the stratosphere in stock form, and modifications are measured exponentially on the dyno. Still today, oil has the overall responsibility of keeping our engines alive through a myriad of operating conditions, and for the most part, has done an astonishingly good job of doing so. The idea that it is still keeping guard over the internal combustion engine’s life cycle after all these decades shows the adaptability and reliability of both oil and engine.

The evolutions through the years to both platforms are an attempt to keep both the internal combustion engine and the oils that preserve them, extant. Ironically, the same could not be said for those critters which originally formulated the organic substances forming the foundation for our engine’s oils. Life and motor oils can be funny that way.

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About the author

Andy Bolig

Andy has been intrigued by mechanical things all of his life and enjoys tinkering with cars of all makes and ages. Finding value in style points, he can appreciate cars of all power and performance levels. Andy is an avid railfan and gets his “high” by flying radio-controlled model airplanes when time permits. He keeps his feet firmly grounded by working on his two street rods and his supercharged C4 Corvette. Whether planes, trains, motorcycles, or automobiles, Andy has immersed himself in a world driven by internal combustion.
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