# Car oil filters are self-tightening? **URL:** \ **Category:** Factual Questions\ **Created:** [August 21, 2024, 12:33am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970 "2024-08-21T00:33:22Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [August 21, 2024, 12:33am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/1 "2024-08-21T00:33:22Z")
I had always learned that you want to just hand-tighten oil filters on your car since it is metal on metal and you certainly do not want to strip any threads. I just heard that oil filters actually get tighter as they work which we all know is empirically correct since you need a wrench to take them off. My question is: what are the mechanics in the system that cause them to self-tighten? ---
**Author:** ![Si\_Amigo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/si_amigo/32/2877_2.png) [@Si\_Amigo](https://boards.straightdope.com/u/Si_Amigo)\ **Post date:** [August 21, 2024, 12:38am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/2 "2024-08-21T00:38:23Z")
> [@Saint\_Cad](#): > > since it is metal on metal Nope, there is a gasket on the oil filter. You don’t want to over tighten or the gasket may deform and allow a leak. ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [August 21, 2024, 12:39am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/3 "2024-08-21T00:39:03Z")
> [@Si\_Amigo](#): > > Nope, there is a gasket on the oil filter. True but the threads themselves are metal on metal. ---
**Author:** ![Si\_Amigo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/si_amigo/32/2877_2.png) [@Si\_Amigo](https://boards.straightdope.com/u/Si_Amigo)\ **Post date:** [August 21, 2024, 12:41am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/4 "2024-08-21T00:41:37Z")
That’s not what causes the seal. And there are compression limiters built into the filter to keep you from deforming the seal and causing the threads to be damaged. Unless of course you used some mechanical advantage type wrench to over torque it down and crush the filter. ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [August 21, 2024, 12:42am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/5 "2024-08-21T00:42:22Z")
I get all that. The question on the floor is how do the filters tighten themselves? ---
**Author:** ![Si\_Amigo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/si_amigo/32/2877_2.png) [@Si\_Amigo](https://boards.straightdope.com/u/Si_Amigo)\ **Post date:** [August 21, 2024, 12:46am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/6 "2024-08-21T00:46:29Z")
When oil contacts the inner ring of the seal, it expands a little more. My dad used to run a ring of oil around the ring for this purpose. ---
**Author:** ![Dogginit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dogginit/32/16920_2.png) [@Dogginit](https://boards.straightdope.com/u/Dogginit)\ **Post date:** [August 21, 2024, 12:47am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/7 "2024-08-21T00:47:45Z")
They don’t “tighten themselves”. Expansion and contraction from heating/cooling make a change over time. How many hot/.cold cycles does an engine (and hence the oil filter/oil filster mount) go through between 3k, 4k, 5k nile oil changes? And sometimes you have dissimilar metals galling that takes place - steel to stainless, steel to aluminum, stainless to steel or aluminum (worst case). ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [August 21, 2024, 12:50am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/8 "2024-08-21T00:50:54Z")
I thought the question on the floor was _if_ they do it? ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [August 21, 2024, 12:56am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/9 "2024-08-21T00:56:01Z")
I presume they do since you need more torque to get one off than it was put on with. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [August 21, 2024, 1:03am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/10 "2024-08-21T01:03:15Z")
The threads may fill with crud and the gasket could get sticky as the oil and rubber degrade slightly. Really, all kinds of reasons. Have you noticed that jars of food are often much more difficult to open after you close them? Same basic deal. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [August 21, 2024, 1:21am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/11 "2024-08-21T01:21:55Z")
> [@Dr.Strangelove](#): > > the gasket could get sticky as the oil and rubber degrade slightly As someone who has done hundreds of oil changes, I think this is the correct answer. For whatever reason, the seal sticks “better” to the engine as time goes on. I am not exactly sure why this is the case, but am guessing it has something to do with heat and the material properties of the seal. ---
**Author:** ![Bullitt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bullitt/32/5725_2.png) [@Bullitt](https://boards.straightdope.com/u/Bullitt)\ **Post date:** [August 21, 2024, 1:27am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/12 "2024-08-21T01:27:55Z")
I always hand-tightened my filters, with a little oil smeared on the rubber gasket. Once the rubber gasket makes contact with the metal, I turned the filter about a half turn. Never too tight. The filters never tightened themselves. When it was time for the next change, the filter came off readily by hand. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 21, 2024, 1:31am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/13 "2024-08-21T01:31:31Z")
I have a theory on this , I will never know if I am right or wrong. When we install the filter it is well lubricated I beieve the lubrication is mostly squeezed out and what remains is possibly absorbed by the gasket making it tighter. My shop would change close to 100 filters per day and I would often get called over when they could not get one broke loose. ---
**Author:** ![Dallas\_Jones](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dallas_jones/32/3277_2.png) [@Dallas\_Jones](https://boards.straightdope.com/u/Dallas_Jones)\ **Post date:** [August 21, 2024, 1:40am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/14 "2024-08-21T01:40:33Z")
> [@Saint\_Cad](#): > > I get all that. The question on the floor is how do the filters tighten themselves? They don’t. Simple answer, flawed question. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 21, 2024, 2:35am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/15 "2024-08-21T02:35:40Z")
> [@Dallas\_Jones](#): > > They don’t. Simple answer, flawed question. It is not a flawed question, they do get tighter. It was not unusual to install a cheater on the end of the oil filter wrench just to break it loose. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [August 21, 2024, 2:40am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/16 "2024-08-21T02:40:09Z")
> [@Saint\_Cad](#): > > I had always learned that you want to just hand-tighten oil filters on your car since it is metal on metal and you certainly do not want to strip any threads. I don’t understand this - most threads are metal on metal. What are you seeing as different here? ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [August 21, 2024, 3:19am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/17 "2024-08-21T03:19:26Z")
> [@Princhester](#): > > What are you seeing as different here? That if you strip threads on the oil filter, you’re screwed ---
**Author:** ![Seanette](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/seanette/32/9139_2.png) [@Seanette](https://boards.straightdope.com/u/Seanette)\ **Post date:** [August 21, 2024, 3:20am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/18 "2024-08-21T03:20:32Z")
> [@Princhester](#): > > I don’t understand this - most threads are metal on metal. What are you seeing as different here? I’m not an expert, but I understand that it’s possible for one set of threads to be a different metal from the other set, which if I understand correctly can cause troubles in automotive applications. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [August 21, 2024, 3:25am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/19 "2024-08-21T03:25:02Z")
IMHO, the average DIYer is 10x as likely to strip the oil drain plug as the oil filter threads. Before the filter gets tight enough to strip the threads, the can would have started to collapse. As for the drain plug - the inane reliance on crush-washers means that the plug needs to be tightened pretty snugly. But, too much is going to be a problem. I always install a Fumoto 1/4-turn drain valve on my first oil change, to make life easier. ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [August 21, 2024, 3:26am UTC](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970/20 "2024-08-21T03:26:35Z")
> [@beowulff](#): > > But, too much is going to be a problem. Changed my oil today. Torque wrench. 29 ft-lb. [Next page](https://boards.straightdope.com/t/car-oil-filters-are-self-tightening/1005970.md?page=2)