# Change oil filter only?
**URL:** https://boards.straightdope.com/t/change-oil-filter-only/262872
**Category:** Factual Questions
**Created:** [September 3, 2004, 12:22am UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872 "2004-09-03T00:22:37Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@mangeorge](https://boards.straightdope.com/u/mangeorge)
#### Post date: [September 3, 2004, 12:22am UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/1 "2004-09-03T00:22:37Z")
Today I read an ad for a car for sale and the seller mentioned that he had a new filter for it, but hadn’t yet gotten around to changing it. I’ve occasionally heard people mention changing their filter, but not the oil.
Old timers I know, most anyway, would never have done this. We might’ve changed the oil and skipped the filter, but not the other way around.
My question is, first, do people actually do that? And second, Have they always done so, and I’ve been living in a bubble all these 59 or so years?
_Not_ seeking opinions as to the wisdom of such a deplorable act, I just wanna know if you or yours do it.
Peace,
mangeorge
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### Author:  [@Berkut](https://boards.straightdope.com/u/Berkut)
#### Post date: [September 3, 2004, 12:27am UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/2 "2004-09-03T00:27:05Z")
> [@mangeorge](#):
>
> My question is, first, do people actually do that?
Yes. When I sold auto parts full time, I used to run into people that did this.
> [@](#):
>
> And second, Have they always done so, and I’ve been living in a bubble all these 59 or so years?
I’ve heard of people doing it for as long as I can remember. I don’t know what their reasoning is, other than just saving money.
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### Author:  [@Dog80](https://boards.straightdope.com/u/Dog80)
#### Post date: [September 3, 2004, 12:35am UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/3 "2004-09-03T00:35:15Z")
I’ve heared of people just changing the oil filter too, but I can’t understand it. It seems to me that the new filter will get “dirty” in no time. 😕
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### Author:  [@olefin](https://boards.straightdope.com/u/olefin)
#### Post date: [September 3, 2004, 12:50am UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/4 "2004-09-03T00:50:42Z")
I think you can find some people that does it… but I wouldn’t think it’s too common in a vehicle.
In my vehicles, oil/filters both are changed at the same time according to manufacture’s recommendation.
For many years I was responsible for large industrial engines and turbines. The equipment would be in operation 24/7 for several years before routine maintenance. The \*\*oil was never changed. \*\* Some may be drained and fresh added if the oil began to show acid. The filters were changed according to pressure drop across the filter.
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### Author:  [@beltbuckle](https://boards.straightdope.com/u/beltbuckle)
#### Post date: [September 3, 2004, 1:10am UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/5 "2004-09-03T01:10:47Z")
I have seen people do this. What they don’t understand is that filters do not filter out everything, and oil breaks down over time.
It has been show, though, that synthetic oil takes much longer to break down than dyno oil, so it does not need to be changed as much. This might be a reason some people would only change the filter.
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### Author:  [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)
#### Post date: [September 3, 2004, 2:59am UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/6 "2004-09-03T02:59:21Z")
Amsoil reps used to claim that their synthetic oil was so good you never needed to change it, just change the filter and add some when needed. Testing by the SAE, IIRC, showed that Amsoil synthetic was actually the poorest synthetic oil at the time, and that all synthetics should be changed at a bare minimum every 12,000 miles due to a breakdown of lubrication and buildup of acids in the oil, along with a steady accumulation of micro-fine abrasive particles. IMO it’s false economy to avoid changing the oil at the same time as the filter and risk additional engine wear - we’re talking about only $5-$25, so why not?
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### Author:  [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)
#### Post date: [September 3, 2004, 3:25am UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/7 "2004-09-03T03:25:06Z")
You must change the filter on a regular basis for obvious reasons. You must _also_ change the **oil** on a regular basis. This is because the oil is contaminated with _not only_ particulates (which the filter gets rid of) but nasty byproducts from the combustion. This includes undesirable hydrocarbons such as **gasoline**. (It’s particularly bad at startup, when the chamber walls are cold and the gas and other crap condenses on the chamber walls and runs down into the oil pan.) The oil filter will not get rid of gas and other hydrocarbons.
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### Author:  [@brad\_d](https://boards.straightdope.com/u/brad_d)
#### Post date: [September 3, 2004, 4:18am UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/8 "2004-09-03T04:18:04Z")
Some folks who dig extended drain intervals using high-end synthetic oils often plan on running the oil, say, 15,000 miles and changing the filter halfway through that. (And then again, obviously, when they change the oil.) Amsoil was the first thing that popped into my head when I read the OP, and I see that Una has already mentioned it. Whether or not it makes any sense to run an oil that long is probably a debate for another thread.
I’ve never heard of anybody advocating never changing the oil _at all_, though - except for the occasional nutjob who is convinced that it’s a Big Oil scam. Those types tend not to be too big on ever changing filters either, though.
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### Author:  [@ralph124c](https://boards.straightdope.com/u/ralph124c)
#### Post date: [September 3, 2004, 10:08am UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/9 "2004-09-03T10:08:04Z")
At every country fair I’ve ever been to there was always a table with some poor schmuck trying to sell this crap! As far as I can tell, ALL motor oils that carry SAE certification are the same…and if you change your oil/filter following the mfgs. directions, you will have no problems. How a little outfit like AMSOIL could produce a better product than a giant like Shell or Mobil , just makes no sense! in fact, I believe that the smaller oil vendors just buy their stuff from the big guys, add a few inconsequential additives, then repackage and sell the stuff. I had a friend who would never buy CASTROL oil (thoughmost foreign car dealers used it). His reasoning was that Castrol (NJ) was one of the largest recyclers of used motor oils…he always believed that castrol oils were a mix of virgin oil and recycled oils.
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### Author:  [@Tangent](https://boards.straightdope.com/u/Tangent)
#### Post date: [September 3, 2004, 12:44pm UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/10 "2004-09-03T12:44:09Z")
> [@mangeorge](#):
>
> Today I read an ad for a car for sale and the seller mentioned that he had a new filter for it, but hadn’t yet gotten around to changing it.
And why does he mention the filter in an ad? Is a new oil filter really that much of a selling point for a car? What do they cost–about 10 bucks? Less?
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### Author:  [@Balthisar](https://boards.straightdope.com/u/Balthisar)
#### Post date: [September 3, 2004, 1:11pm UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/11 "2004-09-03T13:11:22Z")
It’s my experience that when changing the filter, you lose a good portion of the oil. So whether you like it or not, changing the filter gives you at least a _partial_ oil change, unless you run it dry.
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### Author:  [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)
#### Post date: [September 3, 2004, 1:28pm UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/12 "2004-09-03T13:28:30Z")
> [@olefin](#):
>
> For many years I was responsible for large industrial engines and turbines. The equipment would be in operation 24/7 for several years before routine maintenance. The \*\*oil was never changed. \*\* Some may be drained and fresh added if the oil began to show acid. The filters were changed according to pressure drop across the filter.
What do you mean by “large industrial engines”? Big reciprocating diesels? I’m keen to know the details.
I can understand why a turbine can go for a long time without an oil change, it’s because the oil in the bearings is almost completely sealed off from the combustion process. But in a reciprocating engine, it isn’t. The piston rings don’t seal anywhere near as well as the shaft bearing seals on a turbine. Like **Crafter\_Man** said above, the oil gets diluted by unburnt fuel (although diesel isn’t as bad as gasoline), and by the combustion products like water and sulphuric acid.
Anything you can remember about this would be appreciated. 🙂
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### Author:  [@Philster](https://boards.straightdope.com/u/Philster)
#### Post date: [September 3, 2004, 1:59pm UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/13 "2004-09-03T13:59:32Z")
I recall the guide on my Dodge Daytona Shelby Z - which was a turbo - highly recommended oil changes at 3,000 miles and\* oil filter changes every other oil change\*. And I did this.
It was explained to me and I sorta agree) that:
1. the turbo beat the hell out of the oil ( Ok, I can appreciate this general knowledge)
2. a filter is good past 3k - 6k being just fine and dandy
3. even filling the oil filter with oil upon install created brief dips in oil pressure and flow when restarting after a filter change. Turbos being extra sensitive to this were best served by having this happen a minimal number of times. The emphasis was on 3k as a MAX oil life, but that was way ahead of filter time and no good reason to risk oil flow issues.
Anecdotal evidence: I drove a hard 175,000 miles and never had a lubrication related problem. The engine, turbo and all, were outliving everything else. The might have been the only original mechanical bits when I sold it.
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### Author:  [@Alan\_E\_Sheets](https://boards.straightdope.com/u/Alan_E_Sheets)
#### Post date: [September 3, 2004, 3:37pm UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/14 "2004-09-03T15:37:52Z")
I change the filter every 10K and the oil (high temp. synthetic – I’d never do this with standard oil) every 50k. I’ve never had any lubrication-related problems, and I regularly drive cars beyoud 200k.
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### Author:  [@Philster](https://boards.straightdope.com/u/Philster)
#### Post date: [September 3, 2004, 4:05pm UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/15 "2004-09-03T16:05:39Z")
Ever have any failed gaskets, **Alan E Sheets**?
:eek:
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### Author:  [@olefin](https://boards.straightdope.com/u/olefin)
#### Post date: [September 3, 2004, 8:39pm UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/16 "2004-09-03T20:39:15Z")
> [@Desmostylus](#):
>
> What do you mean by “large industrial engines”? Big reciprocating diesels? I’m keen to know the details.
>
> I can understand why a turbine can go for a long time without an oil change, it’s because the oil in the bearings is almost completely sealed off from the combustion process. But in a reciprocating engine, it isn’t. The piston rings don’t seal anywhere near as well as the shaft bearing seals on a turbine. Like **Crafter\_Man** said above, the oil gets diluted by unburnt fuel (although diesel isn’t as bad as gasoline), and by the combustion products like water and sulphuric acid.
>
> Anything you can remember about this would be appreciated. 🙂
2400 HP Cooper-Bessmer natural gas internal combustion reciprocating engines and 10,000 HP Westinghouse split shaft gas fired turbines. All oil was routinely checked with lab analysis monthly for metals and acid. If it showed acid some oil would be drained and fresh added. This was normally not a problem. Natural gas burns fairly clean. During overhaul the oil consoles would be pumped empty, the oil stored, the consoles cleaned and if the oil sample was OK, the oil would be returned to the oil console.
You are correct in your statement.
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### Author:  [@Alan\_E\_Sheets](https://boards.straightdope.com/u/Alan_E_Sheets)
#### Post date: [September 3, 2004, 9:54pm UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/17 "2004-09-03T21:54:41Z")
Never. Why?
> [@Philster](#):
>
> Ever have any failed gaskets, **Alan E Sheets**?
>
> :eek:
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### Author:  [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)
#### Post date: [September 4, 2004, 2:31pm UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/18 "2004-09-04T14:31:10Z")
**olefin** : Thanks for the info, much appreciated.
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### Author:  [@olefin](https://boards.straightdope.com/u/olefin)
#### Post date: [September 4, 2004, 4:10pm UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/19 "2004-09-04T16:10:50Z")
> [@Desmostylus](#):
>
> **olefin** : Thanks for the info, much appreciated.
Your welcome.
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### Author:  [@mangeorge](https://boards.straightdope.com/u/mangeorge)
#### Post date: [September 4, 2004, 6:13pm UTC](https://boards.straightdope.com/t/change-oil-filter-only/262872/20 "2004-09-04T18:13:15Z")
It seems that a lot more people change only the filter than I thought. Huge engines aside, it seems a little foolhardy at best. Especially considering the low cost.
But my faith in humanity has been restored by the preponderance of common-sense replies here.
Danka
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