Let’s face it, we’re living the “good ole days” of automotive ingenuity. Technology is quickly allowing for more power and performance out of the same package that once required a lot of custom tuning and machine work. This is no coincidence, as manufacturers are answering calls by customers and regulators to offer a clean and dependable solution while aftermarket support is pushing those offerings to performance figures not originally envisioned. Maintaining the balance between OEM objectives and the aftermarket will sustain dependability while increasing the likelihood of a fast ride.
Unique Oiling Needs for Modern Direct Injection Engines
In an effort to meet fuel economy standards, Ford launched the EcoBoost engines with a Direct Injection fuel system. Similarly, the recent Gen III Coyote 5.0L V8 also gained Direct Injection while retaining its traditional port fuel injection (yes, dual injection systems). Simplified, Direct Injection just means that during the intake stroke, a fresh charge of air is drawn into the cylinder without its normal dose of fuel from a port injector (or carburetor). Instead, fuel and air are mixed within the cylinder in an abbreviated injection, tumble, mix, and vaporize event. In a dual injection system, the ECU toggles between injection systems to maximize efficiency while meeting driver demanded performance.
Due to the nature of the Direct Injection process, it can be difficult to vaporize fuel within the combustion chamber when RPM is low and load is high. Remember fuel must vaporize, not just atomize, in order for combustion to take place. Whereas a port injected or carbureted engine has time to vaporize fuel while droplets tumble down the intake runners, Direct Injection (DI) engines must inject, mix and vaporize fuel within the cylinder during the intake/compression strokes. This abbreviated cycle leads to unburnt fuel blowing by pistons and making its way down into the crankcase. Ernie Soliz, Sales Director at Torco Lubricants acknowledges the shortcomings of the DI engine cycle and adds “the blow-by issue can be addressed by using a mineral oil (Torco TR-1R) or a blend style oil like (Torco SR-1R Group III synthetic). These products provide improved ring seal when compared to like viscosity in a true high end synthetic.”
In the event that blow-by does make its way past piston rings, fuel has two options; it can vaporize and find its way back to the combustion chamber via the positive crank ventilation system, or fuel can end up emulsified in the engine oil. While neither option is good, having it vaporize is usually more desirable (lesser of two evils).
When fuel finds its way into the oil of the engine, the viscous properties of the oil break down, jeopardizing oils’ ability to protect vital components. Proper oil selection will determine whether that fuel is attracted to or inhibited from emulsifying itself into the engine oil. Once fuel reaches the oil, the mixture can contribute to Low Speed Pre-Ignition (LSPI) issues. Alex Michlberger of Lubrizol Additives describes LSPI as an “uncontrolled combustion caused by higher in-cylinder pressures and lower speed conditions created within the DI engine. This uncontrolled combustion creates spikes in pressure (potentially) causing engine damage. LSPI prevents DI engines from operating at peak efficiencies.” While not directly caused by oil, current theory points toward oil/fuel interaction creating a lower octane gaseous substance that ends up in the combustion chamber, inevitably causing knock due to low octane (reduced resistance to uncontrolled combustion).
LSPI can be mitigated by choosing an oil that has been designed with DI engines in mind. For these oils, proper consideration is given to detergent additives to avoid elements which will promote uncontrolled combustion. Additives such as calcium and sodium are typically minimized while ZDDP and Molybdenum have been found to inhibit LSPI occurrences. Torco’s Soliz confirmed this was understood and that “it is and has been common knowledge for several years that the calcium level may be partly to blame for the LSPI issues. By lowering the calcium level of our SR-1 Super Street Line we have addressed the LSPI issue.”
This begs the question; why can’t these problem-causing elements just be removed from the oil? In an effort to keep the explanation brief, motor oil is simply a base mineral oil with an additive package (let’s stay away from synthetics and blends for the sake of brevity). The base oil carries lubricating properties with it that are desired for keeping moving/rotating parts from contacting each other, inhibiting some oxidation, and transferring energy to perform some controls functions (see Ford Ti-VCT discussion below). The additive package is intended to help supplement the base mineral in performance characteristics that it doesn’t naturally include; detergents, enhanced shear resistance, anti-wear, oxidation inhibitors, etc. As is seen in the LSPI case, these additives can sometimes bring unintended (and negative) attributes which require countermeasures.
Soliz laments over this challenge confirming “building an oil is a balancing act. You take away too much from one area, it effects another area. Primarily, salts of calcium and magnesium are used today as a detergent system. That being said, you cannot lower the calcium too much in a true high performance racing oil. For instance, Torco’s SR-5R and TR-1R contains so much additive system (boundary lubrication additive system for anti-friction and anti-wear, Molybdenum, Phos, Zinc, etc) that it needs a heavy detergent system to control the heavy add pack.”
Special Considerations for a Quiet Overhead Valvetrain
Reflection on the inherent noise generated by the overhead cam designs of the Coyote and EcoBoost engines, Torco’s Soliz suggests giving serious consideration to both the design of the engine as well as the duty cycle you’ll be putting it through before chasing noises. “First, is this a noise that is just inherent in this application? A good quality mineral oil may promote valvetrain noise because it moves slower at cold start-up and when it gets to temp it may eliminate noise.” So if an engine will spend its life making cold ¼ mile passes, oil selection will vary for the same engine built to cruise for any length of time.
When looking beyond peak dyno results at longevity of an engine (whether it be for racing or daily driving) Soliz tends to live by the idea that a little thicker oil never hurt nobody. “If the customer is hell bent on following the rules and is worried about problems down the road, stick with the vehicle owner’s manual that (usually) states 5W-20. I would personally use a 5W-30 or 10W-30 for the life of the engine. The SAE 20, in my opinion, was introduced into this application with environment and fuel mileage credits in mind. It surely was not based on the best protection for your new expensive engine’s upper cylinder and valvetrain.” Personal advice from an oil professional.
Beyond lubricating bearings and helping to seal piston rings from blow-by, the oil in the Coyote engine is being asked to perform hydraulic actuation of its four cam phasers as part of its Cam Torque Actuated (CTA) Twin Independent Variable Cam Timing (Ti-VCT). In this type of duty cycle, oil selection can be critical. “For high temp conditions, a higher viscosity oil, such as the Driven FR-50 can be advantageous for keeping everything pumped up and avoiding hydraulic bleed down,” mentions Driven Racing Oils’ Lake Speed Jr.
Where to Go from Here
So with all of these direct injection overhead cam potholes to avoid, what is a Ford performance junky to do? Start with your homework. In the world of performance oils, LSPI is a hot topic and lubrication companies already have formulations proven to quell detonation. After looking through those offerings, honestly consider what your application is. Drag racing, cruising, and road-racing all have different heat cycles and will put different demands on oil viscosity and additives. Next, consider how often you are changing your oil. Maybe you’re changing oil like you’re changing underwear (hopefully often) and fuel dilution isn’t a concern. Or maybe you want reasonable service intervals between cruise nights. If you’ve made it this far, pick up the phone, call the tech lines and make sure you’re choosing the right oil for your application, there is a lonely tech line operator waiting to steer you in the right direction.