Lubricants Notes from Redline By Roy Howell, Chief Chemist, Redline Synthetic Oil Company, Formerly of Lubrisol 7 April 1992 --------------------------------------------------------------------------- This article covers a wide variety of topics relating to lubricants, including: * Basic Purposes of Lubricants * Refining Crude Oil into a Lubricant * Synthetic Lubricants * Viscosity Index Improvers * Slick 50 * Phomblin * Motor Oil Temperature Limits * Coolants * Automatic Transmission Fluid * Gear Oil * Bearing Grease * CV Joint Lube * Miscellaneous * Recommendations Basic Purposes of Lubricants: 1. Separate Surfaces 2. Removal of Heat (up to 1/3 of combustion heat may be transferred away from engine by oil) 3. Containment of Contaminants 4. Sealing --------------------------------------------------------- Refining of Crude Oil into a Lubricant 1. Refining is the process of removing all the bad stuff. The bad stuff is primarily oxidants. The result of oxidation of the lubricant is first varnish, then it polymerizes into 'goop'. (SA grade oil will goop in 5000 miles) 2. Add Oxidation Inhibitors. 3. Add Detergents. Reacts with oxidized material. Helps keep piston rings clean (Rings are quite hot). Leaves an ash residue when combusted. Not used in airplane engine oils. In an automobile engine, the piston speed (RPM) and therefore piston temperature changes greatly and quickly. The temperature differences allow the ash to break up into small deposits, and go into the exhaust or blow by the rings into the crankcase and lubricants. In an airplane engine, the pistons are operating continuously at a single speed, and therefore do not go through heating and cooling cycles, so the ash deposits would not break up. Generally, for automobile motor, lubricant is limited to 1% ash content. 2% ash is asking for trouble (although 2% may be okay for a diesel engine). Red Line Racing Oils are low detergent. Detergent is left out because ash can cause detonation. 4. Add Dispersants. Dispersants are ashless detergents, which complex low temperature combustion by-products. Dispersants keep partially oxidized particles in suspension, and help keep the engine clean. Dispersants can come apart in extreme high temperature. Average oil filter is a 20 micron filter. Could go down to 1 micron. Stuff that dispersant holds in suspension is much less than microns (it is measured at the molecular level, in Angstroms). At proper temperature, the stuff is not really a problem. Most of the stuff is Aromatic Hydrocarbons, boil around 180 F, and leave through crankcase ventilation. 5. Add Anti-Wear additives. These additives chemically react with iron to prevent welding of moving metal surfaces. Most common additive is ZDP or Zinc Dialkyl Dithio Phosphate. What happens is essentially a chemical polishing of the metal surface. The surface gets plated with either Iron Phosphate or Iron Sulfate, both of which are softer than the base Iron. This chemical reaction occurs in the 300o to 400o F range, and the Zinc is a temperature controlling carrier (controls the temperature at which the reaction occurs. When the two metal surfaces come in contact, a small amount of the surface plating is 'scraped' off of the surface. This is replenished by more ZDP contact with the metal. This action prevents the metals welding through heat generated by high friction contact. The ZDP in the lubricant may last up to 20,000 miles. 6. Add Antifoam. Antifoam is a surfactant, usually silicone, and weakens bubbles. --------------------------------------------------------- Synthetic Lubricants Major Difference is synthetics are not petroleum based. Key Advantages: 1. Volatility: Synthetics do not evaporate as readily as Petro. based. Usually, synthetic lubricants are based on 1 molecule with a flat distillation curve. 2. Better viscosity versus temperature behaviour: a)Thin less as they get hot, b) Thicken less as they cool 3. better oxidation stability 4. Synthetic Oil has 10% better heat transfer than Petroleum based lubricants. --------------------------------------------------------- Viscosity Index Improvers Rubber and Plastic Polymers Start with a base of straight weight Oil. Then add a polymeric thickener. When hot, the long polymer chain is really moving around, causing the oil to flow less. When cold, the polymers stick to each other, essentially coming out of suspension. The polymers are stable up to about 210 F, where they start to break up. The drawbacks to VI polymers is that they can cause engine dirt because of their low shear strength. Viscosity A B C D High | ' ' ' ' | ' ' ' ' |* ' ' ' ' | \ ' ' ' ' | *- ' ' ' ' | *\ ' ' ' ' | *- ' ' ' ' | *\' ' ' ' | *- ' ' ' | ' *\ ' ' ' |-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- | ' *-*\ ' ' ' | ' *\*-*\*-*\*-*\*-*\*-*\*-*\*-*\*-*\ | ' ' ' ' Low |_____________________________________________________________ Low High Sheer Rate A Shear at Piston Rings B Shear at Main Bearings C Shear at Cylinder Wall D Shear at Connecting Rod Bearings -+-+ Viscosity of a Straight Weight Oil (Petro. Or Synthetic) *\*- Viscosity of A MultiGrade Oil (Base with VI polymers) What this chart shows is that a straight oil has the same viscosity regardless of shear rate. However, as the shear rate increases, the shear breaks down the VI polymers, and multigrade oils have less actual viscosity at the localized high shear rate area. The weak link is the rod bearings and cam, in terms of rate of shear. There's less friction at the piston rings. Anti Wear is much more important at the cam. --------------------------------------------------------- Slick 50 Slick 50 does not do anything. According to Roy, to plate Teflon on a metal needs an absolutely clean, high temperature surface, in a vacuum. Therefore, it is highly unlikely that the Teflon in slick 50 actually plates the metal surface. In addition the Cf (Coefficient of friction) of Teflon is actually greater than the Cf of an Oil Film on Steel. Also, if the Teflon did fill in 'craters' in the steel, than it would fill in the honing of the cylinder and the oil would not seal the piston rings. --------------------------------------------------------- Phomblin Phomblin (Another chemical similar to Teflon, used in polishes) is a flouridated ether, has low volatility, is very inert, has low surface tension, and is very expensive. Owned by MontEdison. --------------------------------------------------------- Motor Oil Temperature Limits (oF) 700 ------------------------------------------------------------- | 600 Maximum Useful Range of All Proof Synthetic Motor Oil | | 500 ------------------------------------------------ | --------------------------------- Maximum | | 400 ----------------| | Useful | | Maximum Useful | Maximum | Range of | | 300 Range of | Useful | Diester | | Premium | Range of | Synthetic | | 200 Petroleum | Polyolefins | Motor Oils | | Motor Oils | | | | 100 | | | | | | | | 0_______________________|_______________|_______________|___________| Engine Temperature Chart (F) Upper Cylinder Wall 300 - 500 Exhaust Valve 1200 - 1500 Piston Crown 700 - 800 Hydraulic Valve Lifter 250 - 300 Crankcase 200 - 300 Top Ring 300 - 650 Exhaust Gases 500 - 1000 Combustion Chamber 3000 - 5000 Coolant Jacket 165 - 230 Connecting Rod Brgs 200 - 375 Main Bearings 200 - 350 --------------------------------------------------------- Coolants Red Line Water Wetter is a surfactant - reduces the surface tension of the water. Allows the water to more intimately contact metal. When the water boils, the surfactant makes smaller bubbles, which makes it easier for the bubble to be pushed away from the metal surface, and allow more water to contact the metal. Water Wetter has a high pH, but also has silicates, so it can be used in aluminium radiators. However, if left for a long time, the silicates are depleted, and damage will occur. The liquid versions of Water Wetter do not have phosphates. You *can* cool an engine too much. The ideal temperature for coolant is 190oF. Antifreeze has 1/4 heat transfer capability of straight water. Temperature recordings at block water jacket exit, after stabilizing: Water Anti-Freeze Water Wetter Temperature (F) 50% 50% No 228 50% 50% Yes 220 100% 0% No 220 100% 0% Yes 202 --------------------------------------------------------- Automatic Transmission Fluid Type F - no Friction Modifiers. Ford originally did not want slip in clutch plates. Dexron - GM - less Cf than Type F Now Mercon and Dexron II are almost identical. --------------------------------------------------------- Gear Oil Gear oil viscosity is measured at 150 F vs. 210 F for motor oil. Therefore 40 W motor oil is the same as 95 W gear oil. Gear oil is acidic, motor oil is alkaline. Gear oil needs very high wear protection - Extreme Pressure (marked as EP). Therefore, it has a very high sulphur and phosphorus content. Sulphur and Phosphate reactions start at a lower temperature, and Gear Oil has much more additive than motor oil. This additive is corrosive to copper bearings and bronze synchro rings. Positraction additives are Friction modifiers - make the base oil much more slippery. They coat the metal surfaces, and prevent the stick/slip mode of operation, preventing shudder, and causes smoother take-up. Friction Modifiers may detract from EP characteristics. Friction modifiers cause smooth take-up of Limited slip units. For track racing, FM is probably undesirable, and immediate take-up is more important. For Street, FM is usually recommended for more comfortable operation. Gear oils decompose at lower temperature, usually 250 F. Gear Lubrication Ratings GL-1 No Additives GL-2 GL-3 GL-4 Suitable for light duty hypoid sets GL-5 Has lots of sulphur - Heavy duty hypoids GL-6 Hypoid type gear sets have a sliding rather than rolling action, and therefore require much greater wear protection. GL-5 Should be used in rear differentials. GL-6 is a heavier weight GL-5. Used for heavy trucks and Tow Vehicles. Gear mesh in Gears literally chops up and cuts apart the long polymer chains of Viscosity Index improvers. Smell of gear oil is from high sulphur content. Quaiff Differential is a worm gear, and needs a very slippery oil. --------------------------------------------------------- Bearing Grease Don't fully pack the hub, as it will just overflow. As it turns, the bearing cuts the grease, and oil leaks out. This oil then provides the lubrication. --------------------------------------------------------- Molybdenum in CV Joint Lube Molybdenum in CV joint lube is important in high-angle CV joints, especially off-road applications, where wet lube may be thrown from contact area. The moly provides a dry-film lubrication. --------------------------------------------------------- Miscellaneous Red Line SI-1 - Injector and Valve Cleaner - Removes approximately 1/2 deposits on valve with each bottle. STP is a VI. Castrol R is Castor Oil based. Good lubrication, but dirty. Methyl Lead goes to intake faster than Ethyl Lead. EPA now has authority to outlaw lead entirely. Marvel Mystery Oil and Rislone are surfactants and penetrants. Neo and other Zero Weight oils are actually 0W - 20 multigrade oils, so as soon as they warm up, they are effectively 20 weight oil. --------------------------------------------------------- Recommendations Red Line does not recommend DOT-5 Brake Fluid for racing. More compressible at temperature. Should not use silicone (DOT-5) brake fluid in ABS systems, as there is little to no lubrication for ABS pump. Red Line recommends breaking in an engine on straight viscosity oil. Red Line does not recommend mixing race oil with regular oil. Can use Race Oil for 3 to 4 Events. ---------------------------------------------------------