Depending on who you ask or where you look you could get a few different answers on when you should change your oil. If you want to take care of your vehicle and have it last for many years there is only one answer. It is a lot easier to spend a little money every couple of months than it is to have to purchase a new engine or another vehicle.
How often you should change the oil in your vehicle has been an ongoing debate for quite a while. The "old" saying was 3 months or 3,000 miles, whichever comes first. Yet, when you look in your owner's manual, or sometimes on a sticker under the hood, it might say that you can go 7,500 miles between oil changes. Other people say that if you use synthetic oil that you can go 5,000 to 8,000 miles between oil changes. So who is right? If you look in your vehicle's owner's manual for the oil change interval you will see two things. The first is "normal" driving conditions, and the other is "severe" driving conditions. The manufacturer states that you can go 7,500 miles between oil changes under normal driving conditions, whereas you should change your oil at 3,000 miles under severe driving conditions. Are you a "normal" or "severe" driver? This doesn't just mean are you a lead foot, although that is part of the equation. Most people will tell you that they drive in normal conditions. However, I would say that almost everyone who drives a vehicle drives in severe driving conditions.
So what are "normal" and "severe" driving conditions? Normal driving conditions for the most part do not exist. Normal driving conditions are described as: mostly highway driving on a paved surface in a dust free environment. Severe driving conditions are described as: stop-and-go driving, driving for less than 10 miles at a time, dusty driving conditions, driving in an extremely cold environment, long idling times, and carrying a heavy load or towing a trailer. As you can see, almost everyone's daily driving habits fall into the "severe" category. Let's face it. It's just not possible to drive in "normal" conditions. Therefore, your vehicle will need more frequent oil changes, not the 7,500 miles that you see in your owner's manual under normal driving conditions. That is why I always recommend changing the oil in your vehicle every 3,000 miles. This includes oil changes with synthetic oil. Most people feel that synthetic oil is more expensive and better than regular oil so they can go longer between oil changes. All oil, regardless of whether it is synthetic or not gets old and dirty. You also shouldn't use synthetic oil in vehicles with less than 500 miles, or in vehicles with high mileage. This is due to the fact that the synthetic oil is very slick and in new engines does not allow them to break in properly, and in older/high mileage engines it can easily flow past seals causing leaks.
The best way to look at it is that an oil change is cheap insurance for your engine. It is the most frequently needed service for your vehicle, and one of the easiest to do. It is much better to pay about $30 every 3,000 miles for an oil change than it is to not change your oil often enough and end up ruining the engine in your vehicle and paying thousands to replace it. Simply put, an oil change is cheap insurance for your vehicle, and a service that you can't do too often.
On a side note have you ever wondered why some places that change your oil put the mileage and the date that you had your oil changed instead of the date that you should return for your next oil change? It's quite simply really. A large company was sued by a woman because when she took her new BMW to the company for an oil change, they put her oil change sticker in the window with the 3 months, 3,000 miles on it. After a while of having her oil changed with this company she looked at her owner's manual and found the information about oil change intervals. She sued the company because she ended up having about 5 "extra" oil changes that her owner's manual said that she didn't need. Now a lot of companies simply put the date and mileage that the vehicle was serviced instead so that the vehicle owner can decide if they want to have the oil changed in 3,000 or 6,000 miles, and to keep themselves from being sued. (Yes, people will sue for anything!)