17-24 Race Oils 7/17/13 9:19 AM Page 20
Feature base-oils (Group III, Group IV synthetics and even some Group V oils) to get a higher level of performance. Group IV oils are full-synthetics and include POA (polyalphaolefin) which is the most versatile synthetic. POA does not contain any sulfur, phosphorus, wax or metals. It can withstand elevated temperatures, and has a VI rating of 135 to as high as 300. That’s why POA is used as the base oil in many racing formulas.
Oil Viscosity and Heat Heat is a real challenge in performance engines because the engine may be making anywhere from one and a half to three times as much horsepower than a comparable stock motor, depending on what’s been done to it. That’s a lot of waste-heat going into the block and other engine parts. Direct oil flow to the crankshaft helps cool the main and rod bearings, and splash lubrication helps lubricate and cool the pistons and wrist pins. Add some pin oilers to direct oil at
20 July 2013 | EngineBuilder
the pistons, and the oil takes on even more cooling responsibility. Oil also helps cool the upper valve train, including the rockers and valve springs. Consequently, the oil picks up a lot of heat. The type of oiling system on the motor can help manage much of this heat by routing the oil into a reservoir tank and through an external oil cooler. But engines that are running an internal wet sump oiling system with no external cooler can heat up the oil very quickly in a racing environment. Racing oils are formulated to handle temperatures that cause ordinary street oils to break down. This requires high-quality base-oils and additional friction-modifiers. Many racing oils are designed to handle temperatures in the 250° to 300° F (or higher) range. The oil in a crankcase of a dailydriver is probably going to stay in the 165° to 185° range with normal driving. It can climb higher during hot weather, with sustained high-speed driving, when towing a trailer or
Circle 20 for more information
when driving aggressively. But it is not going to reach the kind of temperatures a race engine can experience. The least demanding racing application as far as oil temperatures are concerned is drag racing. The engine is started cold with little or no warm up time, then it’s a short burnout and a quick blast down the quarter-mile before going back to the pits. The oil never gets very hot, so a relatively thin, low viscosity racing oil such as 5W-20 and 5W-30 may be used without fear of overheating the oil. Thin oils can also be used in certain asphalt circle track engines, too, provided the engine has an adequate oil-reservoir, good oil-cooler and radiator to help manage the heat. Thin oils are typically used with tighter bearing clearances and reduced oil pressure (which saves horsepower). By comparison, more traditional racing oil viscosities such as 15W-40, 15W-50 and 20W-50 are thicker and better able to maintain their viscosity at elevated temperatures in endurance applications such as circle