Change your oil every 3,000 miles:
Once upon a time, this was the case, and many oil companies and lube shops still push this idea. Now, most cars made within the last decade or so require oil changes every 5,000 to 7,500 miles depending on the manufacturer. The better chemical composition and extensive use of synthetic oils, as well as superior engine design, have improved enough to allow for longer intervals between oil changes.
Air Conditioning Harms Your Car's Fuel Economy:
While it's been assumed that running the air conditioner uses up more fuel than rolling down the windows, that's actually not the case. In recent tests, studies have found just a slight decrease in fuel economy and almost no difference when driving with the windows open.
Premium Gas Is the Best:
Busted: If your car doesn't require premium gas, then don't bother filling it up with premium. While it won't hurt your car, it will definitely cost a pretty penny. Most cars actually use regular grade and run just fine. Premium gas has a higher octane level, which means it's less likely to create pre-ignition problems.
Vehicle servicing at independent repair shops will void your warranty:
Your warranty is valid until the expiration date, regardless of where you service your car. Dealerships will imply that you can only go to them, but actually requiring you to do so is illegal. Any maintenance covered under your warranty can be performed by any auto repair shop just save your receipts to prove what was done and how much it cost.
You should replace all four tires at the same time :
Replace individual tires as needed so long as they're the same brand, model, and size as the rest of your tires. You can switch them out whenever. Just make sure to have them rotated at every other oil change to maximize their life.