How many months can a synthetic oil last

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How long, calendar wise, can a synthetic motor oil last in a car. I can go years in the 7,000 MI recommend interval but I thought I remembered that oil should be changed every six months regardless of the miles. That may have been talking about conventional oil though. I took it to the dealership but they said it wasn't due. With $20 oil changes for life they are motivated to keep the changes to a minimum. They don't care if the engine life is reduced but losing money on oil changes is not something they want to do.
 
Depends on too many factors to give a one-size-fits-all answer. While it's generally accepted that a quality synthetic can easily surpass the 12 month mark, the only way to know how long the oil will hold up in your particular engine is to get a UOA done.
 
Not that it represents anything, but I swear someone posted a UOA here of an old truck that hadn't had its oil changed in 2 years and the TBN was still pretty good.
 
Great day... But I think you are right about that... It was like 2 yrs plus and that oil was still good.
 
There was a report with dino hdeo that was looking fresh after many years. 7? Can't remember.
 
Good question. My 2005 motorhome with the ford V-10 gets an oil change every 2 years. Mind you the oil usually only has approx 3000 miles in those 2 years. That's using mobil 1 5w-30 full synthetic oil.
 
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There's a member on here that's got 5 years on Mobil 1.
UOA sample says it's still good.

My 1943 Farmall H has had the same 15W-40 oil in it for around 20 years now. The thing runs perfectly. The Ford industrial engine in my wood chipper has oil that's even older than that, But it only gets used an hour every couple years. (This is all plain "dino" oil, BTW)

It's been proven on here many times - calendar date on oil really doesn't matter.
 
You say regardless of miles. That has to include 0 miles, so it then becomes almost equivalent to the oil shelf life question, except that an engine isn't normally a nominally sealed container.

Valid answers to the shelf-life question are mostly expressed in terms of geological time, or infinity.

Approximately.
 
Well, my Cavalier is sitting at almost 2 years on it's QSUD change.....engine is still doing just fine....
 
It depends upon the conditions under which you put on the miles you do. Suppose every time you drive it, you only go a couple miles. That is not long enough to warm up the engine, have it run lean, and have the oil heat up to cook off moisture. This is even more true in a Michigan winter where you might have to drive quite a while to get the oil up to temperature.

50 trips in this state is much harder on oil than 1, 50 mile trip. It also means starting the engine an additional 49 times, supposedly when engine wear most often occurs and where do these wear particles end up? Either as deformation or more often in the oil.

No it does not need changed every 6 months in "most" cases, but if you were to drive a mile a day every day, "maybe" it needs changed on a yearly schedule.

More to the point, if I were you with low miles, what I would do is "sneak" in an additional oil change between each of the dealer free 7K oil changes. Maybe use the same filter brand so they don't catch on (or don't, that shouldn't really change anything). Don't reset the oil change indicator if the vehicle is so equipped.

It may not be the perfect interval but it seems to make the most sense and still take advantage of the free oil changes.
 
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Depends on driving habits. I go strictly by Oil Life Monitor. The last two times, I have gone 10k miles (about 6 months) each time. But that included a 3k mile round trip in each case. I think there is a big tendency to focus on TBN while ignoring TAN. In general, my vehicle is a short tripper, but the OLM factors that in. I do not have any big trips planned before the summer so it will be interesting to see if the OLM trips sooner this go around.
 
I've used it in my short tripped work van for 2+ years w/o issue. Current fill is going on 19 months, I'll probably change it late summer or early fall. That should put me at about 4K miles.
 
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If one lives in a salt dispersion state, rusty oil filters occur sometimes after a couple years of service. This winter has seen above-average salt dispersion, due to above-average snowfalls here.
 
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