(Courtesy of SKF)įor another example, if a bearing was mounted on a 70-mm shaft rotating at 3,600 rpm, we might assume that the bearing's outside diameter (OD) is twice its inner diameter (ID), or 140 mm. 3 A bearing with a mean diameter of 390 mm at a shaft speed of 500 r/min will require v 1= 13.2 cSt. Required minimum (rated) viscosity v 1 as a function of bearing dimension and shaft speed. Oil overheating may be an additional concern.įigure 2. Oil rings, if used, would probably slow down and malfunction in such viscous oils. But that is unrealistically thick for most process pump bearings. The MRC Engineer's Handbook states, "In general, the oil viscosity should be about 100 Saybolt Universal Seconds (SUS) at the operating temperature." 1 If for some reason a bearing was operating at 210 degrees F, Figure 1 would call for a lubricant with an International Organization for Standardization (ISO) viscosity grade (VG) somewhere between 220 and 320. Whatever the user chooses, he or she must guard against using the thinnest oil found on the market to avoid the problem of inadequate oil film strength and thickness. They can use a jet of oil (oil spray) or convey the oil mixed with compressed air in the form of an oil fog-also called oil mist. Users can heat the oil or avoid oil rings and other risk-inducing lube application methods by using smarter means. Thick oils are more viscous and may not readily flow into the bearings. Figure 1 illustrates where these motor oils fit in comparison to the industrial oil designations used today. But thinner oils, perhaps SAE 10, can help prepare a vehicle for winter driving.
#Mineral oil viscosity vs other oils manual#
What should you use? Check your engine's manual and follow the manufacturer's instructions - always the best bet for long engine life.Some will know from their experience with automobiles that thicker oils, such as Society of Automotive Engineers (SAE) 30, are more appropriate for warm summer months. The Continental Motors engine break-in guide recommends straight mineral oil, while Lycoming recommends AD oil when breaking in all turbocharged engines. However, not all manufacturers recommend this practice. It's thought that mineral oil is less viscous (less slippery) than AD oil, and that it will allow the piston rings to wear in the cylinder walls more quickly. Many pilots have learned to use straight mineral oil while breaking in a new engine. What Oil Type Should Be Used For Break-In "When the engines were disassembled, we found that the piston rings were covered with a gray tacky substance that was primarily made up of the lead by-products of combustion." Read the report here.
At 600 to 900 hours, the engines began to burn more oil and lost compression. Shell Oil tested all-synthetic oils in aircraft engines, and what they found wasn't good. There are some synthetic blend oils used in aircraft engines, but they aren't as common. Unlike mineral and AD oil, synthetic oil is not made from whole crude oil. However, AD oils have added chemicals (additives), which collect debris inside the engine and carry them to the oil filter. Both types are made of mineral oil - a refined, petroleum based oil. There are two main oil types used in aircraft engines: mineral oil and ashless dispersant (AD) oil. Oil Types - Mineral, Ashless Dispersant, And Synthetic We did some research, and here's what we found. There's a lot of discussion about what oil is best to use for your aircraft engine.
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