What causes engine noise after changing to 5w30 oil in a BMW?

[VanMolly]

Possible reasons include the viscosity of the new oil being unsuitable. Detailed explanation: If the oil viscosity is too low, it may not provide sufficient lubrication, leading to increased wear and noise from engine components. Conversely, if the oil viscosity is too high, it can place excessive load on the engine, also resulting in noise. Another possibility is the use of low-quality oil, which can be resolved by switching to a high-quality oil of the appropriate specification. Valve noise: If the engine noise occurs when starting the car in a cold state, it may be due to valve noise. This happens because the car has been parked for an extended period, and the oil pressure hasn't built up yet, leaving the valves inadequately lubricated. The noise should subside shortly. If the noise persists, it could indicate excessive valve clearance or oil leakage at the camshaft, requiring adjustment of the valve clearance or replacement of the relevant oil seals.

[McIsabella]

I remember encountering a similar issue with my BMW before. After changing to new engine oil, the engine started making a ticking noise, especially noticeable during cold starts. The main problem was the oil viscosity mismatch—BMW's precision engines typically require low-viscosity oils like 0W20 or 0W30, while 5W30 is a bit too thick. During cold starts, the oil couldn't flow quickly enough to reach components like the hydraulic lifters, causing increased gaps and resulting in metallic knocking sounds. Another possibility is that the mechanic didn't check the dipstick accurately during refill, leading to an overfilled oil level. This can cause the crankshaft to churn the oil, creating foam and reducing lubrication effectiveness. Don't ignore it—head back to the repair shop immediately to verify the oil grade and, if necessary, drain and replace it. Prolonged use of the wrong oil can also accelerate camshaft wear.

[OColin]

Last month, my neighbor's BMW also had a similar abnormal noise after maintenance, and he asked me to help listen to it. The sound was like metal dry grinding, especially loud around 3000 rpm. The key issue was that the oil viscosity was too high at 5W30. The gaps in BMW's N-series engines are smaller than those in ordinary cars, and if the oil is too thick, it won't flow properly into the hydraulic valve mechanism. Additionally, it was found that he was still using mineral oil, whereas BMWs now require full synthetic oil. Another pitfall is counterfeit oil; cheap oil bought online might be labeled as 5W30 but is actually of poor quality. An experienced mechanic would first read the fault codes to rule out other issues, then drain some oil to check if the level is excessive. Prolonged abnormal noises like this can really lead to cylinder scoring.

[LeAaliyah]

My BMW-owning friends often ask me this. If there's a clicking sound after an oil change, it's likely due to unsuitable engine oil—like pouring honey into a precision watch. BMW engines need thin, water-like oils such as 0W20 for smooth operation. 5W30 is too viscous during cold starts, causing hydraulic adjusters to starve for oil and produce metallic knocking sounds. I've seen repair shops cut corners by using generic oil, only to have the drain plug loosen and leak half a liter. Air bubbles in fresh oil can also cause ticking noises. The worst scenario is using counterfeit oil, where impurities clog the oil pump strainer. If you hear abnormal noises, shut off the engine immediately—calling a tow truck to a professional shop is the safest move.