Choosing oil for your engine has never been an easy decision. So many variables are at play; temperature, load, grade, type, viscosity, and brand are just the tip of the iceberg when one is questioning the right oil for their application. Choosing the correct oil for your high performance machine, in today’s ever changing regulatory environment, is becoming more difficult as the years go on. The American Petroleum Institute (API) has been rapidly evolving to meet the requirements of EPA regulations.
Each stage of this evolutionary process for API certifications (that starburst symbol on the bottle) is strictly for improving fuel efficiency characteristics and reducing a vehicle’s carbon footprint. Most of this is not beneficial for high performance vehicles, with high output engines. So why is over the counter engine oil not as effective as it once was? We will examine what, and why, an engine oil is worthy for performance applications.
Zinc and Phosphorus, or ZDDP, are the two main components that comprise the anti-wear package that exists in engine oil and what creates the boundary layer, or oil film, between mechanical components. Unfortunately these are the two additives that the API reduces, to extend catalytic converter life and efficiency. Since 2010, newest engine oil classification by the API is SN; zinc and phosphorus are limited to 800 ppm and 600 ppm, respectively. With the advancement of mechanical component technology (i.e. not using journal bearing turbos and flat tappet valve train), the necessity of these aggressive additive packages to compensate for mechanical deficiencies has been falling for vehicle manufacturers.
We often see high performance lubricants for engines that have in excess of 1,200 ppm for both zinc and phosphorus. Any engine that employs excessive opening valve spring pressures, use a high lift cam, a journal bearing turbo, and especially those with flat tappet valve train that warrants the necessity for high ZDDP levels. Lake Speed Jr. of Driven Racing Oil says, “the higher you go in lift and spring rate, the more you need the higher levels of ZDDP along with a more active type of ZDDP for maximum protection.” Detergents, or the cleaning agents in oil, work against anti-wear additives so there is a balancing act that takes place. Break-in engine oils commonly, and should, have zero to little detergents allowing ZDDP to do its job during the critical break-in period.
Flat tappet and bucket tappet type engines are notorious for their lube requirement of at least 1,200ppm of ZDDP, or you could possibly “wipe” the cam lobes off through increased friction and metal to metal contact when lacking anti-wear protection. Journal bearing turbochargers also require additional ZDDP, being that they require an oil film to prevent wear and reduce the frictional heat generated. Speed says, “flat tappet engines need more ZDDP, and journal bearing turbos also need ZDDP. However, high lift roller cams need ZDDP as well as high lift overhead cam engines.” Another important additive is Molybdenum, or moly, which is an extreme pressure additive and exists in most premium engine oils.
When moly is present in oil it exhibits microscopic hexagonal platelets that are triggered by the natural thermochemical actions of an engine and stick to sliding parts reducing friction. Moly can resist pressures of up to 500,000 psi before being squeezed out and remains effective for the lubrication of sliding parts while retaining superior oil film strength. Moly also fills all the microscopic pores and cracks in an engine, which is imperative for effective combustion chamber sealing.
Thinner the better
Choosing the correct oil viscosity is essential for engine longevity. Often misunderstood, many enthusiasts either have too thin or too thick of an oil viscosity grade. More often than not, even by misinformed engine builders, the thickest viscosity grade is used in factory performance applications (i.e. 20w-50 for tight/stock clearance engines). However, utilizing oil that is too thick for your application will generate additional heat from the increased frictional drag and also power output will drop. While this argument has its merit, Speed says “high viscosity grades are only necessary in loose clearance applications. When it is possible to run tighter clearances (.001 per inch of journal diameter or less), you benefit from using a lower viscosity oil. In these tight clearance applications, lower viscosity oil runs cooler, reduces start-up wear and improves horsepower output. It is only necessary to run looser clearances in applications where the power density is so great that part deflection requires greater clearances to prevent contact and binding (think top fuel and applications like that)”.
So when choosing your engines’ oil, you should have a general understanding to what makes an equipped performance oil and what oils are derived from EPA requirements. Typically, if not always, the necessary performance oil is not API certified; because it was intended for high output applications. When it comes to oil viscosity grades, follow your manufacturers’ recommendations or follow your engine builders’ advice. Engineers and builders dedicate significant amounts of time, when it comes to choosing the correct oil viscosity.