A cars oil should be changed every 3000 miles, and with that being said the longer you have bad oil running through you're cylinders the shorter the life of that motor will be
No, regular maintenance will allow the car to last longer.
you should change your engine oil in any car when, A. you have driven 3,000 miles since your last oil change, or B. you have gone 3 months since your last oil change. this keeps all of the sludge and dirt out of your oil galleries and off of your bearings and journals... in english, it keeps your engine clean, improves emissions and will keep your car running longer.
form_title= Car Motor Oil form_header= Know your car is in good shape when you change your oil. When was your oil last changed?*= _  How often do you change your oil?*= _  What oil do you use? *= _ 
form_title= Car Oil form_header= The key to keep your car running like is new is to change the oil. What oil do you normally use?*= _  Have you noticed any oil on the ground?*= () Yes () No When did you last change your oil?*= _ 
Your car will not last very long if you don't change the oil at a reasonable frequency. Adding oil does not remove contamination of the existing oil. The bad stuff needs to come out. Time is less important than mileage. Once per year and maybe 6,000 miles are about as far as you should stretch it without oil analysis. It's more important to maintain the level though. If you run a car low on oil it is very bad. If your car is a qt low on oil it only takes 3 more to change it. Cheap way to make your car last longer.
They don't, better oil makes your car run better and last longer
If you are talking about engine oil (which is the oil changed when you get an "oil change"), the answer is no. The oil will pick up contaminates, and the additives in it will break down. As this happens, the oil's ability to provide protection and lubrication to the engine will decrease. If not changed, the engine can wear out or seize up. It is true that some oils can last longer than others, but this only delays the eventual need to change the oil.
form_title=Automotive Oil Change form_header=Keep your car driving for a long time with an oil change! We will help locate a mechanic to change your oil. Have you had an oil change in the last 6 months?= () Yes () No Do you have a particular oil preference?=_ Have you been having any oil leaks?= () Yes () No
form_title= Discount Motor Oil form_header= Keep your car running like new when you change the oil. When was your oil last changed?*= _  How often do you change your oil?*= _  What oil do you use?*= _ 
No you need to still change it fequently, as it still get dirty.
Then that car has a neglected engine that will not last very long and I would not want that vehicle at any price.
Mileage or once each year.