When your fuel economy starts to suck, when the engine idles rough... the easiest sure way is to pull a spark plug or two and look at the electrode.
yeah... if you notice anything different.. Rough idle, poor economy, not pulling as hard as usual. then get it checked out... have the plugs/wires replaced. check all your fluids. You can change all your fluids yourself (can be a bitch though... and dont get rear end oil in your hair or indeed anywhere! the stuff wont come out of your hair and smells like shit). If your asking this question because you think something is wrong then get it checked out... this reminds me im due for plugs thanks!
Look in your "Owners Manual" under routine maintenance or online, but BEFORE you go online look under the hood of your car at the "Emissions" sticker and it will give you the model year and engine size for the car which you need for the correct schedule.
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