The line between obsession and neglect is fine, but walking it properly means you never spend a nickel without a good reason -- and good reasons can include spending money on something that’s not broken. Premium gas instead of regular. Buy the cheapest gasoline that doesn’t make your car engine knock. All octane does is prevent knock; a grade higher than the maker of your car recommends is not a “treat.” 3,000-mile oil changes. Manufacturers typically suggest 5,000 miles, 7,500 miles or even longer intervals between oil changes (many car markers now include oil-life monitors that tell you when the oil is dirty -- sometimes as long as 15,000 miles.) There may be two recommendations for oil-change intervals: one for normal driving and one for hard use. If you live in a cold climate, take mostly very short trips, tow a trailer or have a high-revving, high-performance engine, use the more aggressive schedule. If you seldom drive your car, go by the calendar rather than your odometer. Twice a year changes are the minimum.
Replacing tires when you should be replacing shocks. If your tires are wearing unevenly or peculiarly, your car may be out of alignment or your shocks or struts worn out. Letting a brake squeal turn into a brake job. Squeal doesn’t necessarily mean you need new rotors or pads; mostly, it’s just annoying. Your first check -- you can probably see your front brakes through the wheels on your car -- is to look at the thickness of the pads. Pads thicker than a quarter-inch are probably fine. If your brakes emit a constant, high-pitched whine and the pads are thinner than a quarter-inch, replace them. If your car shimmies or you feel grinding through the pedal, then your brake rotors need to be turned or replaced.