#23 Re: 考大家一个机油的基本常识，估计版上90%的不知道
发表于 ： 2024年 1月 22日 20:53
Quora说的很清楚：同样weight的油，冷的比热的粘。但是现在机油的weight会随着温度变。所以要精确分析，得比较变化率了。
In a multi-viscosity oil, the two numbers don’t translate directly into “flow rates.” Each of these numbers actually refers to a specific viscosity curve; a “5 weight” oil, for instance, in general flows more readily than a “30 weight,” but still flows more readily when hot than when cold. Given the two numbers of a “multi-vis” oil, what you’re really being told (simply put) is that it behaves like a “5 weight” when cold, and a “30 weight” when hot. (There are, of course, specific definitions for all of these, but that’s the basic idea.)
All of those numbers are based on what it would protect the engine like under standard conditions. For example, the 5 in that number, means that the oil will flow and protect your engine, like a 5-weight oil under cold operating conditions upon startup. It is all about viscosity, which is the ability to flow inside the engine, meaning that the thinner the oil gets, the greater its ability to get into smaller spaces.
Obviously, all oils will thin out when they get hot. Once the engine is warmed in winter, then the oil begins protecting your engine as if it was a 30-weight oil.
People commonly call motors oils by “weight.” That is partially correct. They also say, “Thickness.” Basically, it has to do with the properties of the molecules, and their thicknesses ranging from cold to hot.
Many, many years ago, you could not find 5w30, for example. Technology has improved so that the properties of refinement in motor oils makes it very slick and slippery, yet the molecular bonding is dense enough to protect the engine even when warm.
In a multi-viscosity oil, the two numbers don’t translate directly into “flow rates.” Each of these numbers actually refers to a specific viscosity curve; a “5 weight” oil, for instance, in general flows more readily than a “30 weight,” but still flows more readily when hot than when cold. Given the two numbers of a “multi-vis” oil, what you’re really being told (simply put) is that it behaves like a “5 weight” when cold, and a “30 weight” when hot. (There are, of course, specific definitions for all of these, but that’s the basic idea.)
All of those numbers are based on what it would protect the engine like under standard conditions. For example, the 5 in that number, means that the oil will flow and protect your engine, like a 5-weight oil under cold operating conditions upon startup. It is all about viscosity, which is the ability to flow inside the engine, meaning that the thinner the oil gets, the greater its ability to get into smaller spaces.
Obviously, all oils will thin out when they get hot. Once the engine is warmed in winter, then the oil begins protecting your engine as if it was a 30-weight oil.
People commonly call motors oils by “weight.” That is partially correct. They also say, “Thickness.” Basically, it has to do with the properties of the molecules, and their thicknesses ranging from cold to hot.
Many, many years ago, you could not find 5w30, for example. Technology has improved so that the properties of refinement in motor oils makes it very slick and slippery, yet the molecular bonding is dense enough to protect the engine even when warm.
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