![]() ![]() What I have found is that the increased flow with multigrade oil will offset the shear in most bearings that are lubricated hydrodynamically, like crankshafts and cams/lifters. That leads some people to worry that this may result in increased wear over the long haul. But What Affect Will It Have on My Airplane’s Engine?Įarlier I noted that the high pressure in your aircraft’s engine can squeeze the polymer’s long chain molecules and even shear them down permanently, both of which can result in increased flow. These savings can help offset some of the higher price for multigrade oil. The test found that the fuel consumption on the airplanes with multigrade oil was around 4% less than the part of the fleet using Aeroshell W 100. In a year long test at a large flight school, part of the fleet used Aeroshell 15W-50, while another part of the fleet used the single-grade Aeroshell W 100. The improved flow characteristics of a multigrade oil also help reduce the fuel consumption of your engine. This comes from improved oil flow in the ring belt area, which comes from improved efficiency of the oil rings. If your engine has oil leaks or you have loose intake valve guides, then going from a single grade to a multigrade oil will probably increase your oil consumption.īut if you do not have any significant leaks and the main source of your oil consumption is past the piston rings, then you will probably see a 30% to 50% reduction in oil consumption when going from a single grade to a multigrade oil. This brings up the debate about whether switching from a single grade to a multigrade will harm your engine. On the down side, multigrade oils tend to leak more than single grade oils. So, if you have significant leaks in your engine, you can expect more leaking with a multigrade oil. The multigrade oil had oil flow within four seconds, while it took more than 10 seconds for the 100 grade. So that’s a definite advantage for the multigrade oil. In the morning we cranked the engine and measured the time from when we started cranking until we had oil flow to all parts of the engine. We then did the same test with the single-grade Aeroshell Oil W 100. After a short run-up, we let the engine sit in a cold room set at 20☏ overnight. The big advantage for multigrade oil is in cold starting. During one test in the lab, we filled the crankcase of a test engine with Aeroshell 15W-50. This is kind of a good news/bad news thing. Not exactly. You must remember that the viscosity measurement was made using just gravitational pull, but your engine operates at much higher oil pressure. This higher pressure can squeeze the polymer’s long chain molecules and even shear them down permanently, both of which can result in increased flow. If you blend two oils, one a single grade and the other a multigrade with a polymer additive so that both oils have the same viscosity at 100☌, would they both perform the same in a fully warmed-up aircraft engine? These polymers have long chain molecules that shrivel up when cold and then expand when heated. The polymer does not slow the flow of oil at cold temperatures, but expands to reduce the oil flow rate at high temperatures. You can also use a combination of the two methods. ![]() There are basically two routes to blend a multi-grade oil. You can use a synthetic base oil with a super high viscosity index or blend in a polymer additive that works as a viscosity index improver. All aviation piston engine oils are blended with HVI or high viscosity index base oils. In the mineral oil business there are commonly low, medium, and high viscosity index oils. The high and low temperature viscosity are then plotted and the slope of the line is reported as the viscosity index. The oil bath is controlled to 100☌ (212☏) for the high temperature test, but for the low temperature test it varies for different weight oils. In the past, viscosity was reported in seconds, but now it is correlated back to centistokes, an established unit used to measure kinematic viscosity. The time required for the oil to flow out past two special marks is then correlated back to the viscosity. To measure the viscosity of an oil, a lab uses a specially designed test tube. The test oil is put into the tube and the tube is then immersed in a temperature-controlled bath. The bath has a window in the side of it and when the test oil reaches the desired temperature, the oil is allowed to run out. Let’s start with the basics: Viscosity is defined as ”the internal friction of a fluid which makes it resist flowing.” I have written several columns in the past on this, but I will try to shed some more light on the subject. The number one question I receive about lubricants is “multigrade vs single grade, which is best?” Navy Machinists Mate 1st Class Jesse Hinojosa prepares an oil sample for a viscosity and sediment test in the oils lab aboard the USS San Antonio. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |