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What Are Glow Plugs?

Glow plugs may look very similar to spark plugs but there are a number of crucial differences. Firstly, glow plugs are used in diesel engines and spark plugs in petrol engines. Spark plugs are used in petrol engines because the mixture of fuel and air must be ignited, requiring a spark. Diesel engines work slightly different.

Diesel engines work by injecting fuel into a combustion chamber containing highly compressed air. The air is compressed to such a degree that under normal circumstances it is very hot. So hot in fact, that the injected fuel spontaneously combusts as soon as it comes into contact with the air. However, in colder weather the combustion chamber isn’t always able to reach the required temperature threshold without assistance. That’s where glow plugs come in.

Glow plugs are effectively small electric heaters. An electrical current is delivered to the coil tip of the glow plug, known as the heating element. As the electrical resistance begins to build, the coil starts to emit heat and glow, hence the name. With the compressed air in the combustion chamber at a more suitable temperature, the injected fuel will combust and the engine can start. The time it takes for the chamber to heat up will depend on the starting temperature of the engine and the ambient temperature.

Keeping on top of your glow plug maintenance is vital for running a healthy and efficient engine. Fail to do so and you could run into trouble come winter. Deteriorating or failed glow plugs won’t be able to counteract the effect of cold temperatures on the engine’s combustion chamber and you’ll be stuck going nowhere. One of the major causes of failure in glow plugs is the extreme changes in temperature they undergo. Just like spark plugs, each diesel engine cylinder requires its own glow plug. For this reason, a single faulty glow plug may not have a noticeable impact on your car’s performance. However, once a few glow plugs have deteriorated, you’ll certainly see a difference.

We Offer The Best Glow Plugs

The Green Spark Plug Company stock a wide variety of glow plugs including ‘hard to find’ part numbers. We offer a wider variety of brands, including Champion, DENSO, Durite, NGK and Bosch glow plugs. Some of these are well-known historic brands who offer the perfect fit for classic car models, but we also carry brands who cater for modern vehicles.

It can be difficult to find glow plugs for vintage cars but not at The Green Spark Plug Company. We’ve been collecting and building up our stocks of unused glow plugs for over 40 years, so we’re confident that we’ll have what you’re looking for. To find out, simply input your vehicle details into our glow plug finder below and we’ll find the best glow plug for you.

Lodge set up Motorcraft and their racing plugs are still
favoured by many of Tim’s friends today. Spark plug technology has been developed and refined for well
over a century, adapting to the differing needs of manufacturer specifications. Whether you have a personal favourite brand or are completely new to the world of spark plugs, we have
anything you could possibly need.

Our Glow Plug Finder

Our glow plug part finder will help you find the right glow plug for your diesel vehicle. Our glow plug finder features all popular glow plugs from trusted brands including Denso, Durite, Champion, NGK and Bosch

Remember, if your vehicle is petrol or LPG then use our Spark Plug Finder instead.

Spark Plugs Part Finder

Our spark plug part finder will help you find the right spark plug for your petrol or LPG vehicle. Our spark plug finder features all popular spark plugs from trusted brands including Denso, Bosch, Champion and NGK. 


Remeber, if your vehicle is diesel then use our Glow Plug Finder instead.