Another simple replacement item: spark plugs. Well, simple on most vehicles. Replacing your spark plugs can have a dramatic effect on fuel economy, especially if they’re old and worn out. Spark plugs have come a long way in the past few years. It used to be that you changed them out about every 10K to 30K. These days, most plugs go 100K or more. Part of the reason for this is that vehicle manufacturers are trying to keep their advertised maintenance costs down. The funny thing is, although they have increased the replacement interval for spark plugs, the cost of these longer-life plugs has gone up quite a bit.
The best place for answers about what plugs are in your vehicle and when you should replace them is your vehicle’s service manual. Some vehicles list the type of plug they want used on the under-hood emissions sticker. I would strongly suggest you stick with this recommendation. I’m not an advocate of using different spark plug brands or types different from what the manufacturer calls for. It seems the engineers designed the ignition system around a particular spark plug, and I’d wager they did that for a reason. If you use a different type of spark plug in your engine, you run the risk of going outside the ignition system design, which could affect your fuel economy. I know there are spark plugs that claim to give you better mileage and more power, but don’t you think that if that were really possible they’d already be in your engine from the factory?
So if your plugs are old, replace them. When you do replace them, use the plugs recommended by the manufacturer for best results. Aside from using different spark plugs, old spark plugs can affect your engine’s performance. As plugs get old they can misfire and cause incomplete combustion. A misfiring engine is not an efficient engine, and efficiency is what we want for the best fuel economy.