True or False: Change Your Oil Every 3,000 Miles

Natalie Josef
September 29, 2010

An apple a day keeps the doctor away. Breaking a mirror brings seven years of bad luck. Eating carrots improves your eyesight. A watched pot never boils. If you swallow gum, it will live in your belly forever. We’ve all heard these old wives’ tales since we were little, but which ones should we believe and which ones are simply fairytales?

As far as car-related old wives’ tales go, none is more enduring than the recommendation that you must change your oil every three months or three thousand miles—whichever comes first. Obviously, your car won't grind to a halt if you wait until your 3,001st mile to change your oil, but does this adage hold true? And if so, are you damaging your vehicle if you wait too long?

Is it true?
Like most things in life, this advice has some truth and some fiction. Before carburetors started to be replaced with fuel injection, engine oil was prone to breaking down either from mechanical wear or fuel saturation. These two problems lead to overfueling, and the fuel would leak down the cylinder walls and into the oil pan. After about three months or 3,000 miles, so much oil had accumulated that its ability to properly lubricate moving engine components was severely compromised.

When fuel injection rolled around, less fuel was wasted and more sophisticated engine management systems were able to increase engine operational temperatures, which permitted efficient combustion with leaner mixtures (less fuel per portion of air).

Additionally, rising crude oil prices led to the creation of smaller engines, which required thinner oil viscosity. These changes increased the life of engine oil—since the oil was breaking down at a slower rate, it didn’t need to be changed as often. Manufacturers began to increase the time between oil changes from 3,000 miles to 5,000 miles to 10,000 miles and beyond.

In 1996, Consumer Reports did a study on NYC cabs and found that even under the most grueling driving conditions, there was no difference between changing the cabs’ oil at 6,000 instead of 3,000 miles. Additional studies and anecdotal evidence further supports the fact that in modern cars, changing the oil at 3,000 miles is not only unnecessary, but throwing away perfectly good oil is harmful to the environment.

What should you do?
When in doubt about anything concerning your vehicle, consult your owners manual. The manufacturer knows your car’s engine better than anyone, and will provide you with specifications concerning when to change your oil, what oil to use, and other pertinent information. Also, most modern cars come with a warning system indicator light that will alert you when it is time to change your oil.

You also need to consider your driving habits. If you venture out to the grocery store once a week and that’s about it, you can certainly push the oil change back a few months, though you should change your oil at least once a year. If you have a penchant for driving up steep inclines in first gear while towing a horse trailer in the middle of the desert, your oil will break down much quicker and you will need to change it more often.

Engines are designed to work best when fully warmed up and oil has a harder time absorbing contaminants when it is cool. A daily highway commute of twenty miles is much easier on your engine than running errands in town. The short trips prevent the engine and oil from fully warming up.

The bottom line
It never hurts your car to get its oil changed, but since everything is so darn expensive these days, we all need to save money whenever we can and changing your oil at 3,000 miles when your owners manual says 5,000 miles is a waste of money. After all, a penny saved is a penny earned—that adage will never change.


Natalie Josef

About the Author

Natalie Josef is an automotive expert at RepairPal, the leading online source of auto repair resources and estimates. With many ASE Master certified mechanics on staff who have decades of experience, RepairPal knows all the fine points of car repair.

1 User Comment

Sign in to comment
By , April 19, 2013
I have a 2006 PT Cruiser. How often does the oil need to be changed?