Since i drive with the engine off so much, my plugs tend to turn into solid lumps of carbon over time:
This (when it gets bad enough) makes the engine run badly, so i made a little kit consisting of some metal brushes and a prod:
In a minute or so you can make a plug good as "new":
Happy (well running) motoring!
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__________________
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2016: 128.75L for 1875.00km => 6.87L/100km (34.3MPG US)
2017: 209.14L for 4244.00km => 4.93L/100km (47.7MPG US)