I hear some people say that too thin of an oil can spin a bearing, is there any truth in that statement? Also, is it better to have more oil flow or more oil pressure? From what I understand, oil flow is very important at startup, however, from what I got out of it, flow is good for lowering temps, acting as a cooling system. But under normal conditions, is it better to have a thicker oil at normal temp?
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Oh #@$%!, not a question that cannot be answered. Guy, there is no one answer to you questions. You talk in such generalities, exactly what answer are you looking for????
If you hear things, and then we say something else, then do you suddenly believe??? Why don't you get specific, and talk about the car you are talking about? the engine size? The milage? and so on.. Other than that, don't pose such silly stuff on here...
If you hear things, and then we say something else, then do you suddenly believe??? Why don't you get specific, and talk about the car you are talking about? the engine size? The milage? and so on.. Other than that, don't pose such silly stuff on here...
As I understand it the engine requires enough flow to for the hydrostatic "cushion" and cooling. How much pressure is required to accomplish this will vary with design. In other words the pressure is a "result" of the requirement not a requirement itself.
Well I'm more or less asking about answers for most vehicles in general. I realize certain conditions can change what specifications need to be met. And I am not exactly looking for ONE answer, #@$%! a whole list of them would be great. I'm just looking to expand my knowledge. But you do make a good point, an application to narrow things down would help. I realize in new vehicles that there is no oil too thin. I suppose what I mean is, in OLDER vehicles, ones that werent built with the whole 5w-20/30 specs. in mind, is there a truth to an engine spinning a bearing from thin oil, or any # of internal engine problems that could develop from too thin of an oil in an older application? BTW, I don't post if I know my question can be looked up easily in past threads, or if I can use my common sense to get an answer. So if my current questions are silly than so be it.
If you use a lube without the correct hydrodynamic properties and no barrier lubricant properties, I suppose you could "spin a bearing" Take canola oil for example. So maybe go thicker - Crisco. But with most any modern motor oil, it's not going to happen - or extremely remote.
As for your last statement - read on, young grasshopper. You flitter from spot to spot never stopping to take in the wafts of knowledge. There is much to be gained by patience and open eyes.
As for your last statement - read on, young grasshopper. You flitter from spot to spot never stopping to take in the wafts of knowledge. There is much to be gained by patience and open eyes.
Be it that I have no data to pass on to you, I will put this that "I'm beginning to think"...that newer engine designs that specify Xw-20 oils may have clearances that are likely nothing new, but whose surface finshes are finer, reducing surface heights of asperities. Though it could be thought to be of some trade-off to reasoning for the use of an oil of decreasing viscosity (increasing operating efficiency and perhaps even adding in cooling/enabling better thermal equalibrium with what people say are hotter running engines - higher output/decreasing size), bearing surface area may have also increased slightly to further compensate and ensuring a safe operating clearance through the designed load/rpm range of the engine.
As for spinning bearings, I think of oil starved situations. The dynamics that could conclude such could be caused by too little oil infeed in repect to outbleed, which in itself could be result of high local temperatures that causes thermal thinning of the lubricant, too high infeed oil temperature/too thin a viscosity. Excess sustained loads with clearances that are in spec, or with clearances that are in excess, could thus enable contact that would exacerbate localized heating and potentially create a runaway situation - thermal thinning, increased outbleed, increased part contact, increased thermal expansion, debri churning, welding...siezure???
I think using too thick an oil could also cause starvation issues that might lead to spinning a bearing, as I recall a question of whether or not to start a dozer in sub zero weather conditions with the case filled with 10w30 petroleum oil. Granted this points to oil circulation at cold start-up as the oil pump goes to bypass due to such a high viscosity value at the temps given, resulting in insufficient/too long a delay for oil circulation to meet the requirements of the bearings, loads, and rpm conditions.
It's all very dynamic, which fascinates me, even if my concepts are a little off - I welcome correction!
Take care everyone.
As for spinning bearings, I think of oil starved situations. The dynamics that could conclude such could be caused by too little oil infeed in repect to outbleed, which in itself could be result of high local temperatures that causes thermal thinning of the lubricant, too high infeed oil temperature/too thin a viscosity. Excess sustained loads with clearances that are in spec, or with clearances that are in excess, could thus enable contact that would exacerbate localized heating and potentially create a runaway situation - thermal thinning, increased outbleed, increased part contact, increased thermal expansion, debri churning, welding...siezure???
I think using too thick an oil could also cause starvation issues that might lead to spinning a bearing, as I recall a question of whether or not to start a dozer in sub zero weather conditions with the case filled with 10w30 petroleum oil. Granted this points to oil circulation at cold start-up as the oil pump goes to bypass due to such a high viscosity value at the temps given, resulting in insufficient/too long a delay for oil circulation to meet the requirements of the bearings, loads, and rpm conditions.
It's all very dynamic, which fascinates me, even if my concepts are a little off - I welcome correction!
Take care everyone.
How about 0w30 AmsCriscozoil......
Sorry....I meany 0w30 German Crisco......
Yes, if the oil is too thin the crankshaft can rub on the bearing with such force that the bearing index key is torn and the bearing moves in its journal. It is also possible that too thick an oil can do the same. Consider a thick oil at low temperature. Start up an engine and immediately go WOT. Here the oil is sufficiently thick that when the piston develops a large force, that the oil in the bearings becomes stiffer than the bearing material itself! in this case, the oil becomes "metalic" and the bearing spins due to friction-weld-up. Oil must be in the correct range of viscocities for the bearing/crancshaft interface to have a long life.
Yes, but too thin in this context would have to be accompanied by various qualifications. The oil can be thin because it has a spec of -50W-(-10) and is like water at room temperature; or the oil could be thin because it is a normal weight (0W-30) but at a high temperature (350dF).
The thin/thick you are looking for is actual viscocity (10 centiStokes) not the weight of the oil (10W-30).
It is better to have both set properly. Really wide clearances at the bearings will result in more flow than the pump can pump, leading to oil starved bearings. Really anrrow clearances can result in maximg out the pump pressure with insufficient oil flow accross the bearings.
Aside from keeping metals from contacting other metals, oil carries away heat. This is vitally important in high stress situations (race engines) but remains important in every day engines. So, flow is important.
Pressure at the oil pump is specified so that there is adequate flow at startup when the oil is thick, and than after the engine is well warmed up and operating under heavy loads, that the oil flows through the bearings at a rate sufficient to keep the bearings at safe temperatures.
It is always better to have engine oil at 8-to-10cSt--unfortunately we lack the ability to manufacture oils that have 10cSt of viscocity at every conceivable temperature. Thus oils are designed to be as thin as possible at startup, and remain sufficiently thick at extreme temperatures.
In addition, the substances used to create a "nicer" viscocity curve (thin when cold, thick when hot) have some "less than stellar" properties with respect to shear. So, moderation of viscocity index improvers is also in the oil specification mindset.
Great answer from both Curious Kid and Mitch Alsup.
It's especially heartening to see surface finishes mentioned too.
If you wish to delve deeper into this subject, here's an online lecture that'll get you started into the basics of hydrodynamic bearing design.
http://www.utm.edu/departments/engin/lemaster/Machine Design/Lecture 26.pdf
It's especially heartening to see surface finishes mentioned too.
If you wish to delve deeper into this subject, here's an online lecture that'll get you started into the basics of hydrodynamic bearing design.
http://www.utm.edu/departments/engin/lemaster/Machine Design/Lecture 26.pdf
Thanks for the link...and the "pat-on-the-back." Speaking for myself, this all seems a systematic and synergistic marvel...which I suppose is what fascinates me.
Purely anecdotal... every spun main or rod bearing that I have had personal experience with has been due to an empty or almost empty oil pan or a broken oil pump shaft. The one instance of broken oil pump shaft was due to over revving a cold engine, a thinner oil may have prevented this. Or maybe it was just a weak shaft.
I have never seen a spun cam bearing, though I know that this can happen.
Rickey.
I have never seen a spun cam bearing, though I know that this can happen.
Rickey.
I think Fred0803 needs to take a pill, any question on here is interesting if you give it time, If you dont like the question move on. Theres a wealth of knowledge to be had on this site. How many people think we are all stupid talking about oil so much? My wife and kids being among them.
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