Posted on 11/28/2025
Gasoline and diesel engines burn fuel in very different ways, which is why they use different plugs. Spark plugs make a timed spark to ignite a fuel and air mix in gas engines. Glow plugs warm the diesel combustion chamber so compressed air is hot enough to ignite injected fuel cleanly, especially on cold starts. Understanding how each works helps you spot issues early and choose the right service. Spark Plugs: Timed Ignition for Gas Engines A spark plug sits in the cylinder head and fires an electrical arc across its electrodes at just the right moment. The ignition coil charges, the plug sparks, and the air-fuel mixture burns from that point outward. Heat range, electrode design, and gap size are matched to the engine so the plug stays clean and the spark is strong at idle and under load. When plugs wear or foul, the arc weakens, misfires increase, and fuel economy drops. Glow Plugs: Preheating for Diesel Combustion Diesels ignite fuel by compre ... read more