Why does the idle speed drop after switching to full synthetic oil?

[AuroraAnn]

There are several reasons for the lower idle speed after an oil change. Improved lubrication: Changing the oil enhances the lubrication inside the engine, reducing wear on internal components, which naturally leads to a lower idle speed. Excessive oil addition: The amount of oil replaced in the car should be slightly below the mark on the dipstick. Too much oil increases the rotational resistance of the crankshaft, reduces the engine's power output, and allows excess oil to enter the combustion chamber, leading to oil burning, blue smoke emission, and increased fuel consumption. When adding lubricating oil, it is best to keep it slightly below the mark on the dipstick. Introduction to car oil changes: If there is too much oil, the excess can easily enter the combustion chamber (due to high internal pressure) and form gummy carbon deposits. Although there may be no obvious effects initially, over time, the carbon deposits will become increasingly severe, not only causing idle speed fluctuations but also clogging the catalytic converter's pores, leading to excessive exhaust emissions (increased fuel consumption). In severe cases, oil burning may occur. Choosing the right oil for your vehicle is crucial. Selecting oil with too high a viscosity will definitely affect its flowability.

[Mateo]

I remember after switching to full synthetic oil last time, my car's idle RPM dropped directly from 900 to 750, and the engine felt smoother when driving. Talking about this change, it's mainly because full synthetic oil has lower viscosity and better fluidity, which reduces internal engine friction. The ECU detects smoother operation and automatically lowers the RPM to save fuel. This is normal as long as the idle is stable without shaking, indicating the oil change was worthwhile. But if the RPM drops too low or there's a trembling sensation, pay attention to possible spark plug aging or a dirty air filter - a quick check will give peace of mind. During regular maintenance, choosing the right oil viscosity is crucial, and full synthetic's extended service life can also prolong engine lifespan.

[DiIsabelle]

As someone who enjoys tinkering with cars, I've noticed that switching to full synthetic oil often leads to a drop in idle speed. The reason is simple: the superior performance of new oil with lower friction coefficients reduces engine running resistance, prompting the ECU to lower idle speed for improved efficiency. This change is usually harmless—stable idle speed even saves a bit of fuel. However, if the drop is excessive or accompanied by abnormalities, it might indicate faulty sensors or throttle carbon buildup. My advice is to drive a few hundred kilometers first to observe before deciding whether to check the wiring. High-quality oil like full synthetic does benefit engines, as its cleaning properties help maintain engine condition.

[Calvin]

After years of car repair, I've seen this quite often. Switching to full synthetic oil lowers idle speed because the oil is thinner and flows better, reducing friction which naturally drops the RPM. The ECU adapts to this adjustment, so as long as it's stable, there's no need to worry. However, if the drop is too significant, say from 800 to 600 RPM, it's worth checking the spark plugs or for any air leaks. If everything runs fine after a while, then it's all good.

[DeCharlotte]

I just changed to full synthetic oil, and the idle speed dropped a bit, from 850 to 800 RPM. After some research, I found that full synthetic oil has lower viscosity, which reduces engine resistance, so the ECU lowers the speed. It feels quieter during normal driving and also saves fuel. However, if the RPM fluctuates significantly, it might be due to a faulty mass airflow sensor or ignition issues. Remember to check it promptly to ensure safety.