Another thing to remember is that maintenance intervals may vary with the type of replacement parts which are used. Spark plugs and synthetic oils are two good examples of this. Although we have suggested changing your oil and filter every 3,000 miles, use of a synthetic oil may allow you to lengthen or even double this mileage, IF your usage fits the proper patterns (highway miles, above freezing, with little stop-and-go and no excessive speeds . . . ). The recommendation we give for spark plugs is based on conventional plugs with an electronic ignition system, which probably covers most vehicles on the road. If you have an antique that uses a points ignition, well then you will probably have to replace the plugs more often. But, if you use special plugs, like the increasingly popular long-life Platinum plugs, you may easily be able to double the recommended replacement interval. The key here is to pay attention to the directions supplied with your replacement parts (and if you have never replaced an item before, check with the manufacturer for suggestions about original equipment).