Car care doesn't come cheap, but for the most part, it's money well spent. After all, you need safe, reliable transportation, and you can't have that if you don't take care of your car. But there are some common pieces of car care advice that most people have heard that don't really help your car at all. In fact, they may be costing you extra money. Take a look at the truth about these car care myths.

Warm Your Car Up Before You Drive

Before you put the car in drive and take off, let it idle for several minutes so that the engine can warm up – especially on a cold or snowy day. Have you heard that one before? It sounds like something that should be true, which is probably why most people don't question it. However, it turns out that this advice is not only wrong, it's bad for your car, and it's bad for the environment too.

As it turns out, the engine warms up much more quickly when you actually drive it than when it's sitting in the driveway idling. You should only wait between 10 and 30 seconds after turning the engine on before you start driving lightly. Idling the car wears your engine out faster, which can lead to expensive engine repairs. Plus, your car produces the most pollution when it's idling, because the catalytic converter doesn't kick in properly until the engine is fully warmed up.

Use High Octane Fuel

When you go to the gas station to fill up, which pump do you choose, the cheapest one, or the one with the highest octane rating? If you pick the high octane gas, it's probably because you've heard that it will give you better gas mileage, or that it will be better for your car.

The truth is that all the octane rating tells you is whether or not the fuel is likely to detonate prematurely, causing the engine to knock. Lower octane fuel is more likely to detonate prematurely. But wait – before you decide to keep filling up with the more expensive fuel, consider this: most of today's vehicles were designed to run on the lowest octane fuel and won't benefit from higher octane. Unless your owner's manual specifically calls for a higher octane rating, stick with the 87 octane.

Change Your Oil Every 3000 Miles

You've almost certainly been told that an oil change needs to happen every 3000 miles. If you've been driving for long, you've probably gotten this advice from at least one mechanic. You may even have a little sticker on your windshield right now, reminding you change the oil once you hit the next 3000 mile mark.

However, the truth is that today's synthetic oils can last a lot longer than 3000 miles. Most manufacturers recommend changing the oil at 7500 or 10,000 miles, and some let you go as far as 15,000 miles. That means that you may be changing your oil up to five times too often, and throwing money out the window on those oil changes. Check your service manual to see how often the manufacturer recommends changing your oil, and stick with that schedule to save money (and oil).

Save money by avoiding these car care myths, and that way you'll have the cash for auto repair services and maintenance that you really do need.