oil change frequency

I recently bought a used Mits Galant '00. It did not come with a owner's manual, so I bought a Haynes Manual for it. It says oil should be changed every 6 months. Is that what everyone does? I know 3 mo/3k miles is the standard, why would Haynes Manual say 6 months? thanks to all in advance.

it depends on the oil asweel, if its semi or fully sythetic your putting in

A good rule of thumb for 4 cylinder engines is every 5000 miles. This, of course, is under normal driving conditions. High engine revving, dusty climate, mountain driving, or stop-and-go driving do not count as normal here. For these conditions, or for larger V6/V8 engines, stick to every 3000 miles.

At the very least, check your oil every 3K on the odometer to see how it looks. If it's dark or black, change it! If you think you will let your car go beyond 3000 miles, use a partial or fully synthetic oil. And always use the viscosity recommended by the manufacturer! Mitsubishi recommends 5W-30 for -20F to 100F degrees. If you live in a hotter climate that never sees temps below 0F degrees, you can use 10W-30. This will help with breakdown as temperatures pass 100F degrees.

Hope this helps!