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What is the difference between glow plugs and spark plugs?

Charlotte Phillips, 1 month ago

3 min read

  • Advice
  • what
Glow plugs

WhoCanFixMyCar discusses the difference between glow plugs and spark plugs, including the common symptoms of failure and average repair costs.

Difference between glow plugs vs spark plugs

What happens when a glow plug or spark plug fails?

How much does it cost to replace glow plugs vs spark plugs?

How often do you need to replace spark plugs?

How often do you need to replace glow plugs?


What's the difference between glow plugs and spark plugs?

First and foremost, both glow plugs and spark plugs are the ignition source in a combustion engine. However, the different types of engine that the two are found in is what makes them unique to one another.

While spark plugs are found only in gasoline engines, glow plugs are found only in diesel engines. Therefore, it’s quite easy to determine which one your car requires should you ever need to get it repaired.

What happens when a glow plug or spark plug fails?

When glow plugs and spark plugs fail, the symptoms of the two are very similar to one another.

Glow plug and spark plug failure will ultimately cause problems with your engine to occur, from engine misfiring, to reduced fuel mileage and loss of power.

How much does it cost to replace a glow plugs vs. spark plugs?

The average cost to replace glow plugs vs spark plugs is generally very similar. According to our records, the average cost to replace glow plugs is £179.61, versus £122.20 for spark plugs when booked through WhoCanFixMyCar.

How often do you need to replace spark plugs?

Spark plugs are built to last, therefore you should expect to get anywhere between 80,000-100,000 miles out of them before they begin to show signs of failure.

How often do you need to replace glow plugs?

As with spark plugs, your glow plugs should also last you up to 100,000 miles before showing signs of failure. 


If you think you might need your glow plugs or spark plugs fixed, there are a number of mechanics in our network who can carry out the repair for you. Simply enter your registration plate and postcode on the homepage to get a quote from a specialist near you.