What Causes Engine Knocks and Pings?
When someone complains about having a noisy engine, most of the time they’re talking about annoying knocks or pings or other similar sounds.
Whatever word you use to describe the noises, they are usually caused by improper engine detonations. “Detonation” may sound like a major problem by itself, but technically your engine runs on detonations. Little explosions of fuel inside the cylinders are what drive your engine and provide the power for your car. It’s only a problem when the detonations come at the wrong time – either before or after the cylinder is designed to spark them – or if they fail to burn up the fuel completely.
In most cases, the root cause of the problem is the fuel itself.
You might think that all gasoline is the same, regardless of where you choose to fill up, but that’s actually not the case. Some gasoline is higher-quality, with additives and conditioners designed to prevent buildup and keep your engine burning fuel cleanly. But many stations sell lower-quality gasoline, without the additives. As a consumer, it’s hard to know the difference. Even if you only buy lower-quality gasoline part of the time, eventually it will lead to engine deposits that can cause knocking sounds. And these knocking detonations actually cause more deposits to build up, so it’s a self-perpetuating problem.
Gasoline also comes with different octane ratings, which is another way in which fuel quality differs. A low octane rating can cause knocks or pings, especially in a high-compression engine.
Note that octane and additives are completely different things. High-octane gas from a station with low-quality fuel will still be low-quality. And low-octane gas from a high-quality station will still have low octane.