* Severity of the knock: A light, occasional knock might not cause immediate catastrophic damage, but it will accelerate wear. A severe, constant knock is far more destructive and can lead to engine failure much sooner.
* Cause of the knock: Is it detonation (caused by improper air/fuel mixture, timing, or low-octane fuel), or a mechanical issue (like a rod knock or a spun bearing)? Mechanical knocks are far more serious and typically indicate imminent failure. Detonation can be managed (by addressing the root cause), but unchecked will lead to damage.
* Driving habits: Continuing to drive with a knock significantly increases the damage. The harder you drive, the faster the damage will accumulate.
* Engine maintenance: A well-maintained engine might tolerate some knocking for a longer period than a neglected one.
* Engine design and material: Some engines are more robust and can withstand knocking for longer than others.
In short: Driving with a knock is extremely risky. It's not a matter of "how long" but rather "how much damage" before failure. You could experience damage within minutes, hours, days, or perhaps weeks, but it's highly unlikely to last for months or years. The knock is a clear warning sign that something is seriously wrong and needs immediate professional attention. Continuing to drive with a knock will almost certainly lead to expensive repairs or a complete engine failure.
