# Oil change frequency



## shari (Dec 27, 2004)

I'd like some help settling an argument about how often the oil should be changed in the average car. Some say it's 3 months or 3000 miles whichever comes first. Others say that 3/3000 info was good back in the day but with the new and improved oil used today it's more like 1yr or 7500 miles. What are your opinions on the subject?


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## twajetmech (Jul 1, 2004)

As an Aircraft mechanic/instructor let me dispel some of those notions for you. Yes, you should change your oil every 3000mi....the actual date is not so important. Now, there are basically 2 types of oil, Petroleum, and Synthetic. Petroleum based oils (Penzoil, Quakerstate etc) are excellent, but, during the cumbustion process the oil picks up some of the particulate matter produced. This, over time causes the oil to become slightly acidic, and "wears out" the additive package (due to heat). Petroleum oil also does not keep the particulate matter in suspension, thus without frequent oil changes (3000mi) that starts to build up in the engine case as sludge. There is more on it but I think thats enough for now. Synthetic based oils, hold up better to heat, keep the particulate matter in suspension longer. But just like Petroleum based oils the additive package eventually "wears out" over time. So, its easy enough and cheap enough to simply change the oil every 3000mi and keep the engine as clean as possible, and well lubed with fresh oil. Now, the reason people say you can go for a year or 7500mi on Synthetic is because they feel that its superior lubricating properties and better heat qualities mean they can get away with less frequent oil changes....this is only true if you have really good filtration. The filtration on your car is not up to the task of cleaning the Synthetic oil and removing the particulate matter as say an Aircraft filtration system....(we don't actually change oil....we simply add to whats there and change the filters every 25-50 hours !.....this refreshes the additive package and keeps the oil clean, but our filtration is much much better than the avg auto, to the point that the filters do such a good job the oil never really changes color !.....your automobile system was not designed to do that) Thus knowing now the properties of Synthetic, frequent oil changes removes much more of the sludge and particulate matter and keeps the additive package fresh. Either way it is preferable to change the oil every 3000mi regardless of the type of oil used. Note, however....for a high milage car, you can not switch from using Petroleum based oils to Synthetic or vice-versa without an overhaul....the seals and "O"-rings have been conditioned under that type oil and will break down if a new oil type is introduced...
If you'd like a more indepth discussion let me know


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## Rashiki (Sep 29, 2005)

Arguing over the frequency of oil changes is like arguing over which is better, Chevy or Ford, Intel or AMD. You're not going to get a clear cut response.

Both sides of your argument have valid points, as oil has come a long way from back in the day with the additions of synthetics and improved detergents/friction additives. 

Engines have also come a long way with different oiling systems and such to make oiling more efficient.

I am old school thinker and like to change the oil in my vehicles every 3000 miles, eventhough i use a synthetic blend in my sports car, and regular oil in my truck.

Frequency will change dramatically with driving situations/habits/enviroments. Harder driving, a lot of stop and go, dusty conditions warrant more changes. The opposite requires less. I suggest you go with what the manufacturer recommends in your service manual eventhough people will tell you that they just want to sell oil. 

Remember, oil is the lifeblood of your vehicle!!


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## JamesO (Mar 30, 2005)

Oil is cheaper than steel!

It is way cheaper to keep a clean engine than to repair, rebuild or replace the engine due to an oil related failure!

If you really want to extend the length of your oil change, you need to install a bypass oil filter.

http://www.amsoil.com/storefront/bf.aspx

http://www.bypassfilter.com/

These filters continuously filter the oil down to a few micros, eliminating almost all abrasive particles. But these are sometimes rather large and hard to install in compact environments. These tend to be more of a convenience in situations where downtime to change oil is hard to find. But they do work well and do allow increasing the oil change interval.

At the end of the day, the real governing factor for determining oil change interval is not time, mileage or hours, it is a function on how a vehicle is driven, the environment the vehicle is driven in and the total number of engine revolutions that have been completed. An hour meter is close for fixed RPM engines in industrial situations, however, this is not so accurate for over the road applications.

The problem is none of the vehicle manufacturers have a device that counts the number engine revolutions that I am aware of.

In the end, basic math can probably solve this problem.

Assumptions - Oil change cost $25, vehicle driven 100,000 miles
Oil changed every 3,000 miles - 33 oil changes in 100k miles for a cost of $825.00
Oil changed every 7,500 miles - 13 oil changes in 100k miles for a cost of $325.00

Would you rather spend $500.00 for additional oil changes or would you rather risk spending much more for major engine repairs? How far will $500.00 go toward a major engine repair? 

I know how I would spend my money!

You be the judge!

JamesO


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## bruiser (Jul 30, 2005)

Why not ask the experts: http://theoildrop.server101.com/cgi/ultimatebb.cgi


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## Tumbleweed36 (May 14, 2005)

bruiser said:


> Why not ask the experts: http://theoildrop.server101.com/cgi/ultimatebb.cgi


Hi,

I found this link very interesting and informative. Frankly, I didn't know about this source for that kind of information.

However, I think we did ask the expert when twajetmech went through what I thought was the best explanation of all of them. His hands on experience from a variety of engines and knowledge about their needs and operation was very exempliary and informative treatise on what should be done.

I too am a 3000 mile oil changer and have been for years, although in my early years, was one of those 2000 mile changers of oil products. When I was a kid many moons ago, 2000 miles was the recommendation (darn, I just told my age) for oil changes. The newer engines iMHO, now make it so you can wait until 3000.

Hey all, have a great day.


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## crazijoe (Oct 19, 2004)

I change mine every 3K miles on the daily drivers. My collectible cars (I have 5 of them) will get an oil change right before I put them in for winter storage. Regardless of milage. I have changed oil in one of my collector vehicles with only 800 miles on the oil change. I don't like the thought of dirty oil sitting on the bearings all winter long.


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## Tumbleweed36 (May 14, 2005)

Hi,

Good idea Crazijoe. Those babies aren't throw away cars like the ones I drive. Can't blame you for protecting your investment. Wow, five of them, an independently wealthy person. :sayyes: ray:


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## crazijoe (Oct 19, 2004)

Tumbleweed36 said:


> an independently wealthy person. :sayyes: ray:


Yea... I wish. 
I have a hard time getting rid of "old muscle".


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## Tumbleweed36 (May 14, 2005)

I know what you mean. Still have my eye on an old 55 Chevy, but probably will never get it.


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## Rashiki (Sep 29, 2005)

Any of those 'Old Muscle' Camaros?


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## crazijoe (Oct 19, 2004)

1970 Oldsmobile Cutlass SX
1971 Oldsmobile Cutlass SX Convertible
1954 Ford F100 P/U (All Original down to the 6V positive ground electrical system)
1979 Chevy Short Box P/U with an Olds 425CI 
1972 ElCamino SS (yes, a legit SS. No fakes here)(wifes car)


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## daamon_vexion (Aug 6, 2006)

*drool*


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## Tumbleweed36 (May 14, 2005)

Hi,

Uncle, I have a very sad story to tell you. I had one of those 1972 ElCamino SS, vehichles years ago. I am telling my age, but it was a car that we just used around like the rest of the cars. That one was a great one and I had not planned on getting rid of it. Well, here is the story,

One of my sons asked if he could take it to a school function since my wife was using the car he normally would be permitted to drive. I foolishly said yes, with the stipulation that he not let anyone else go with him and that he go there and come straight back with no side trips. 

Well, as kids go (he was 17), he did go straight there to band practice. A friend of his asked if he would take him home since it was raining when practice got out. A dark night with rain, he consented. My son knew he had to hurry since I knew when the practice was out and I would expect him home at that time. You know, I would never know about the little side trip if he hurried.

He was coming home fast in an area of town he didn't know very well, on a street he rarely had been on, saw a car pull out in front of him, wet leaves on the road since it was a hard rain, and he wiped out two newer vehicles parked along the side of the street. My insurance ended up paying for two newer cars that he hit when he slid. 

Unfortunately, this was a car that I had paid for in cash about three weeks earlier, so didn't worry about anything except PLPD insurance since I was the only one who usually drove it. I lost the car (basically he totaled it, but not injured), my insurance went up big time since he hit two newer cars and wiped them out, and to this day, miss that darn car or truck (I called it a Cluck at that time since it was half car, half truck in my mind) That care IMHO was made like a tank and lucky for that or he would have been injured.

Darn, I would give a lot to have that old car back, but life doesn't work that way. Needless to say, when the police dept. called to tell me about the accident, I found out about his little "side" trip. Still kick myself for letting him take that little beauty that night.


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## Midnight Tech (Dec 31, 2001)

Straight from the folks at the Car Care Council :


> The best advice is to follow the guidelines provided in the vehicle owner's manual, but every 3,000 miles or 3 months is a good rule of thumb for oil and filter changes.


This is what most manufacturers refer to as "severe service schedule" and is actually the way most vehicles are driven (stop and go driving, short trips, etc.).


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## daamon_vexion (Aug 6, 2006)

hehe hot dusty conditions with an overweigh vehicle


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