Spark Plugs And Fuel Efficiency

Apart from having to be clean in order to start a car, do spark plugs have an effect on petrol consumption? I haven't changed mine in a while and the car seems to be heavy on petrol at the moment.

Yes is the quick answer.. Many reasons why, dirt, gapping, not fitted correctly.

From a friends [broken link removed]

SPARK PLUGS
Why
Spark plugs supply a spark in the combustion chamber to ignite the fuel/air mix in a petrol engine. A worn spark plug can cause incomplete burning of the fuel/air mix and have a negative effect on engine performance and emissions test. Spark plugs in bad condition are also related to problems such as hard starting and misfiring. A new set of spark plugs will not only help emissions and performance but improves fuel economy too.


When
The standard spark plugs (Copper) will need to be changed once a year to maintain peak engine performance. Some more modern cars come with long life spark plugs (Iridium) fitted which can last up to 100,000 miles. The down side to Iridium plugs is that they are more expensive to replace. On some cars access to spark plugs may be a problem, in this case it is a good idea to use long life spark plugs.

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Thanks for that info, Ronan. Good link too!