Why does the engine warning light come on after an oil change?
3 Answers
There are many reasons why the engine warning light comes on after an oil change. The causes of the warning light coming on include the following: 1. Oil type: Engine oils produced by different manufacturers cannot be mixed. When changing to a different brand of engine oil, the engine should be cleaned to prevent the old and new oils from reacting and affecting the oil quality. If the old oil is not completely drained and is incompatible with the new oil, it may cause the warning light to come on. 2. Residual old oil: If the residue from the old oil is not thoroughly cleaned, the new oil may not last long, clogging the oil filter and causing the warning light to come on. Changing the oil filter during the oil change can also eliminate the factors that cause the warning light to come on. 3. Oil filter: Some oil filters are of poor quality and have inadequate oil filtration performance. Replacing the oil filter during the oil change can also eliminate the phenomenon of the warning light coming on.
After changing the engine oil, the check engine light comes on, which could be due to several reasons. From my experience repairing many vehicles, common causes include a loose oil filter or a leaking seal ring, leading to insufficient oil pressure and false sensor alerts. Incorrect oil levels are also frequent issues—overfilling causes excessive oil pressure while underfilling results in low pressure, both triggering the light. Additionally, using the wrong oil grade may cause the engine control module to detect anomalies and trigger a warning. I recommend first checking the dipstick to ensure the oil level is near the midpoint, then verifying if the filter is properly installed. If the issue persists, it’s best to visit a repair shop to read the fault codes with a diagnostic tool, as other underlying problems might be hidden.
Last month, right after I changed the engine oil in my car, the warning light came on, which really made me nervous. Turned out I had slightly overfilled the oil - after draining some out, the light went off. It could also happen if the filter wasn't tightened properly, allowing air to enter and cause pressure fluctuations. My friend's car had a similar issue that was actually caused by a loose sensor connection. Generally speaking, as long as there's no oil leak and the car drives normally, there's no need to panic. First check the oil level and filter installation yourself - if that doesn't solve it, get a professional mechanic to take a look. Don't delay too long to avoid engine damage.
