為什么換完機油后發動機的聲音更大了？
Why does the engine sound louder after changing the oil?
1.機油過量
1. Excessive engine oil
機油加注也是有標準的，并非是越多越好，如果機油加注量過多，對曲軸旋轉工作產生更大的阻力，從而影響動力輸出，增加油耗。進入燃燒室的機油量大大增加，使燃燒室內積碳增多，增加了活塞運動阻力，使發動機功率下降。同時也會造成燃燒室空燃比發生變化，增加爆震的幾率，噪音也會隨之加大。
There is also a standard for oil filling, not the more the better. If the oil filling is too much, it will produce greater resistance to the rotation of the crankshaft, thus affecting the power output and increasing fuel consumption. The amount of oil entering the combustion chamber is greatly increased, which increases the carbon deposition in the combustion chamber, increases the piston movement resistance and reduces the engine power. At the same time, it will also cause the air-fuel ratio of the combustion chamber to change, increase the probability of detonation and increase the noise.
2.中度積碳
2. Moderate carbon deposition
老機油越用越稀，積碳越來越多。機油稀了容易竄機油，造成積碳越來越多。當換上新機油時，發動機不能適應機油粘度，可能會拉高轉速，進而造成發動機噪音大。建議用高標號汽油開高轉速，建議保持開2500轉以上開一箱高標號油應該就有改善，當然也可以進行預防性清洗。
The old engine oil is thinner and thinner, and carbon deposits are more and more. When the engine oil is thin, it is easy to channelle the engine oil, resulting in more and more carbon deposition. When the engine is replaced with new oil, the engine cannot adapt to the oil viscosity, which may increase the speed and cause loud engine noise. It is recommended to use high-grade gasoline to drive at high speed. It is recommended to keep driving more than 2500 rpm. Opening a box of high-grade oil should be improved. Of course, preventive cleaning can also be carried out.
3.機油粘度要適合
3. The oil viscosity shall be suitable
不同等級的機油有著不同的特性，其低溫啟動性和高溫的抗磨、附著性也有著不同的表現。機油的黏度與溫度呈反比的關系，當發動機冷態時，機油黏度較高，若選用的機油較稠，便會給啟動馬達、電瓶等增加額外的損耗。但若機油過稀，在高溫工作下則難以形成足夠的保護膜而引起潤滑不足，導致機件加大磨損。如果車輛手冊建議5W-30，而車主要用5W-40的那發動機噪音變大，那么車主就需要注意了。建議選機油建議是車輛手冊推薦的標號。
Different grades of engine oils have different characteristics, and their low-temperature start-up and high-temperature anti-wear and adhesion also have different performances. The viscosity of the engine oil is inversely proportional to the temperature. When the engine is cold, the viscosity of the engine oil is high. If the selected engine oil is thick, additional losses will be added to the starting motor and battery. However, if the engine oil is too thin, it is difficult to form sufficient protective film under high temperature operation, resulting in insufficient lubrication and increased wear of parts. If the vehicle manual recommends 5W-30 and the vehicle mainly uses 5W-40, the engine noise becomes louder, then the owner needs to pay attention. The recommended engine oil is the grade recommended in the vehicle manual.
4.機油混加
4. Oil mixing
這種情況也比較常見，由于不同品牌用的技術配方不同，可能會產生不良化學反應，改變其本身自有的特性，從而對發動機造成磨損，噪音增加。建議車友們建議不要混加機油，盡量使用同一品牌的機油。如遇特殊情況更換不同品牌機油，建議使用同標號機油。
This situation is also common. Due to different technical formulas used by different brands, adverse chemical reactions may occur and their own characteristics may be changed, resulting in engine wear and increased noise. It is recommended that motorists do not mix engine oil and try to use the same brand of engine oil. In case of special circumstances, it is recommended to replace oil of different brands with oil of the same grade.
5.遇到假機油
5. False engine oil
這種情況也是很有可能出現的，由于新手司機在給自己的愛車做保養時，加入了劣質的機油。由于“假”機油它的抗磨、清潔、潤滑保護等性能都非常差，導致發動機壓力過大，從而磨損加劇、噪聲加大。作為消費者，對相關的防偽知識要知道一些，不能只道聽途說，要懂得如何辨別機油的真偽。
This situation is also likely to occur, because novice drivers add inferior engine oil when maintaining their car. Due to the poor anti-wear, cleaning and lubrication protection of "fake" engine oil, the engine pressure is too high, resulting in increased wear and noise. As consumers, they should know some relevant anti-counterfeiting knowledge, not just hearsay, but how to distinguish the authenticity of engine oil.
6.冷車聲音大正常
6. The sound of cold car is loud and normal
冷車狀態機油大部分都回流到油底殼，這時候發動機內部器件缺少潤滑，冷車啟動的時候發動機溫度還會變低，機油的潤滑性能也達不到好的狀態，加上發動機預熱轉速的原因會造成噪音偏大，但熱車后噪音轉速又會降下來了，這個是正常情況。如果熱車后沒有恢復正常，建議大家去檢查一下。
When the engine is cold, most of the engine oil flows back to the oil pan. At this time, the internal components of the engine are lack of lubrication. When the engine is cold, the engine temperature will become lower, and the lubrication performance of the engine oil can not reach a good state. In addition, due to the preheating speed of the engine, the noise will be too high, but the noise speed will drop again after the hot car. This is a normal situation. If it doesn't return to normal after hot driving, I suggest you check it.
7.心理作用
7. Psychological function
這個應該是占大多數，人的聽力在不同的環境是有誤差的，單憑耳朵是不能判定聲音變大的，建議用分貝儀測量。從油品粘度的技術角度分析，5W-20、5W-30的機油在市區行駛中噪音會稍微大些，在高速正常行駛，噪音會稍小些。5W-40、5W-50的油品在市區行駛中噪音會稍小些，上了高速正常行駛，噪音會稍大些。
This should account for the majority. People's hearing has errors in differe