time based oil changes?

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NH73

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First it was the 3month/3000 mile oil change. Then miles were pushed, and pushed even more with synthetic oil. A lot of oil change places still stick to 3 months, some auto or oil manufacturers say 6 months, synthetic says a year. I have found this article by Amsoil: http://www.amsoil.com/newsstand/motor-oil/articles/why-is-there-a-time-limit-on-motor-oil/

I seen numerous sources say the same thing, but no one has proof to show this actually happening. As anyone done UOA's on low use oils to know that the oil needs changing after a said amount of time?
 
I've often said time is the about the only thing you need to be worried about. Just change your oil every 6 months for conventional, and 1 year for synthetic. Period. Simple as that.
 
Originally Posted By: CrawfishTails
I've often said time is the about the only thing you need to be worried about. Just change your oil every 6 months for conventional, and 1 year for synthetic. Period. Simple as that.


A good many knowledgeable people on this forum would dispute that assertion.
 
Originally Posted By: NH73
I seen numerous sources say the same thing, but no one has proof to show this actually happening. As anyone done UOA's on low use oils to know that the oil needs changing after a said amount of time?

I've done a UOA after 16 months (two winters). TAN was already exceeding TBN, and the lab condemned the oil.

This OCI included significant amount of short tripping though. If you don't short trip, time may not be as much of an issue.
 
Originally Posted By: teddyboy
Originally Posted By: CrawfishTails
I've often said time is the about the only thing you need to be worried about. Just change your oil every 6 months for conventional, and 1 year for synthetic. Period. Simple as that.


A good many knowledgeable people on this forum would dispute that assertion.


By definition, if you short-trip a lot, you don't accumulate miles very fast, so 6 months (or 1 year synthetics) works for that. If you long-trip it, you get more miles, yet by definition you have just made trips where the oil warms up thoroughly, so 6 months or 1 year again works just fine.
 
I left German Castrol in my 08 Mustang for 4 years and 16k miles. I've been meaning to send the sample I pulled in but haven't.

I don't think I've ever changed the oil in my generator in 18 years. I don't remember if I used synthetic.
 
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I've never gone by time. Not once. I would spend thousands of dollars a year on service if I went by time rather than mileage. Conventional oil might degrade with time whether it's used or or not, anything synthetic shouldn't matter unless you get into ridiculous non-use like 1000 miles a year or something.
 
I think I might change the QSUD in my cavalier this year...in april it will be two years.
 
Last edited:
Originally Posted By: Quattro Pete
Originally Posted By: NH73
I seen numerous sources say the same thing, but no one has proof to show this actually happening. As anyone done UOA's on low use oils to know that the oil needs changing after a said amount of time?

I've done a UOA after 16 months (two winters). TAN was already exceeding TBN, and the lab condemned the oil.

This OCI included significant amount of short tripping though. If you don't short trip, time may not be as much of an issue.


The last few months of mine became more short trips, but before that they oil got to warm up...

The oil is still clean, but it does have me wondering about the TAN...
 
I don't worry about time in service, as long as I'm able to get the oil up to temperature regularly. I just change it based on mileage, regardless of time. If it was short tripped all the time, I'd scale back more towards the time factor. The Firebird I handle a bit differently since I store it for the winter and prefer to have fresher oil in it so I tend to schedule the oil changes in that vehicle more based on the seasons.
 
Originally Posted By: NH73
First it was the 3month/3000 mile oil change. Then miles were pushed, and pushed even more with synthetic oil. A lot of oil change places still stick to 3 months, some auto or oil manufacturers say 6 months, synthetic says a year. I have found this article by Amsoil: http://www.amsoil.com/newsstand/motor-oil/articles/why-is-there-a-time-limit-on-motor-oil/

I seen numerous sources say the same thing, but no one has proof to show this actually happening. As anyone done UOA's on low use oils to know that the oil needs changing after a said amount of time?


Yonks ago, Mobil, once they finally understood that my 4Runner was out of warranty stated that 12 months was fine, 5,000km (3,000 miles) or 40,000km (25,000 miles) on 0W40M1.

That being said, I've gone over 18 months to get 10,000km OCIs up on my diesel Nissan and have had no issues.

Some other alternatives, some based on science, and some lapsed BITOGers here

http://www.brianschreurs.org/neptune.spacebears.com/cars/stories/interval.html
 
I don't understand the 1 year overall limit by the oil manufs. How can oil degrade just sitting around? TBN doesn't affect ability to lubricate so I'm not that concerned about that. The biggest thing intuitively for me is soot settling out and causing problems. My completely drained filter felt very heavy. It was probably clogged with carbon.
 
Originally Posted By: OneEyeJack
... and don't forget changing oil based on fuel used.

Just as long as it's a reasonable number.

In case of my BMW, the OLM is set to 2375 liters (627 gallons), which is a little steep. If I'm mostly short tripping and get horrible fuel economy of 16 mpg, that still translates to 10,000 miles. At the rate I accumulate miles, that's about 5 years in service. Then again, other than a few UOAs, I don't really have any proof that this would make my engine self-destruct before I was ready to part with this car.
 
Originally Posted By: turtlevette
I don't understand the 1 year overall limit by the oil manufs. How can oil degrade just sitting around? TBN doesn't affect ability to lubricate so I'm not that concerned about that.

Oil gets exposed to outside conditions and oxidizes. It also gets exposed to moisture and fuel that naturally happen during start/stop cycles and warmups and cooldowns. Over time, this causes the oil to become acidic and it starts to eat away at your engine.

Not saying 1 year is the magic number when this becomes an issue. But time is a factor.
 
IMO, cars that are stored in a garage and don't get driven much can go many years without a change. Outside with the wide temperature extremes might be a different story. I haven't personally ever seen a problem with old oil, I have seen problems with low oil or no oil.
 
They say one year as 'a safe conservative time' that accounts for worse case senario. Using standard filtration. Bypass filtration is a different story.
 
You'd think that the amount of time/distance people go between oil changes around here, oil prices would have dropped do to supply and demand factors. No one seems to be doing the three month 3,000 mile interval anymore. Most go at least twice that and many are going much further...yet no price change despite oil consumption/use being cut in half???
 
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