Can you replace an oil filter without changing the oil

Joined Oct 6, 2018

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372 Posts

Discussion Starter · #1 · 12 mo ago

Is it possible to change the oil filter without draining the oil? I've had a vehicle with a top mounted filter before, but always drained before removing so I'm wondering what would happen if the filter was removed with with a full oil level.

Joined Mar 8, 2020

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1,378 Posts

Yes, it's certainly possible to change the oil filter without draining the oil sump. As long as the engine is off, there is no oil pressure and you should not lose any oil during the change, except for the small amount that's in the filter.

Even with an engine with the filter down low, it's never truly at the bottom of the sump. It's always on the upstream side of the oil pump, so the only oil you actually lose is the small amount of oil in the filter and the small amount of oil in the galleries above the filter. You can still change the filter without draining the sump; you will not "drain the sump" through the open oil filter adapter.

Can you replace an oil filter without changing the oil

2021 Ascent Limited Black/Black

Joined Nov 17, 2020

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678 Posts

Is it possible to change the oil filter without draining the oil? I've had a vehicle with a top mounted filter before, but always drained before removing so I'm wondering what would happen if the filter was removed with with a full oil level.

Just curious, but when would you want to change the filter but not the oil? I'm not a car guy, so I know virtually nothing, but I've heard of changing the oil but not the filter, but not the other way around. What would be the advantage of just changing the filter?

Joined Oct 6, 2018

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372 Posts

Discussion Starter · #4 · 12 mo ago

Even with an engine with the filter down low, it's never truly at the bottom of the sump. It's always on the upstream side of the oil pump, so the only oil you actually lose is the small amount of oil in the filter and the small amount of oil in the galleries above the filter. You can still change the filter without draining the sump; you will not "drain the sump" through the open oil filter adapter.

Yeah, I wasn't concerned about risk of draining the sump so much as I was about removing the filter and making a big mess in the engine bay. I was thinking there should not be much oil in the filter if I let the car sit a few days but wanted to make sure I wasn't overlooking something.

Just curious, but when would you want to change the filter but not the oil? I'm not a car guy, so I know virtually nothing, but I've heard of changing the oil but not the filter, but not the other way around. What would be the advantage of just changing the filter?

That's a very fair question. I went to the dealer to look into a few issues, among them was increased oil level. They agreed that it was slightly above the max line and did a drain and fill of the oil, but did not replace the filter. I'm close to an oil change interval, and figured if it can be done without creating a huge mess that I would replace the filter now since the oil is fresh.

Can you replace an oil filter without changing the oil

2021 Ascent Limited Black/Black

Joined Nov 17, 2020

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678 Posts

That's a very fair question. I went to the dealer to look into a few issues, among them was increased oil level. They agreed that it was slightly above the max line and did a drain and fill of the oil, but did not replace the filter. I'm close to an oil change interval, and figured if it can be done without creating a huge mess that I would replace the filter now since the oil is fresh.

Yeah, that totally makes sense.

Joined Apr 18, 2020

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204 Posts

I do my own servicing and have found Subaru’s top mounted filter to be laughably easy to change. You can do it with minimal mess by unscrewing the filter enough to let any oil drain out but only unscrew it enough so it doesn’t flood the dish that it sits in. If there is any dirt or other contaminants in there you don’t want them washing down into your engine. Before I do anything i give it a good wipe in there with a shop towel but I also keep a ziploc bag over the filter with an elastic band holding it on snugly and my dish is nice and clean. I also prefill my filters a bit when installing a new one and you can flip it over and thread it on quickly enough that there is no spillage. This method soothes my OCD!

2022 Ascent Onyx, Ice Silver

Joined Oct 29, 2021

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820 Posts

Just curious, but when would you want to change the filter but not the oil? I'm not a car guy, so I know virtually nothing, but I've heard of changing the oil but not the filter, but not the other way around. What would be the advantage of just changing the filter?

I am taking delivery of my new Ascent today. I intend to follow the break-in procedures, and also change the filter at around 500 miles. My reasoning is that any residual machining swarf will be trapped by the filter, while the oil itself will still be fresh. Just to satisfy my curiosity, I'll cut open the filter and see how much of whatever has been trapped.

2022 Ascent Onyx, Ice Silver

Joined Oct 29, 2021

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820 Posts

I do my own servicing and have found Subaru’s top mounted filter to be laughably easy to change. You can do it with minimal mess by unscrewing the filter enough to let any oil drain out but only unscrew it enough so it doesn’t flood the dish that it sits in. If there is any dirt or other contaminants in there you don’t want them washing down into your engine. Before I do anything i give it a good wipe in there with a shop towel but I also keep a ziploc bag over the filter with an elastic band holding it on snugly and my dish is nice and clean. I also prefill my filters a bit when installing a new one and you can flip it over and thread it on quickly enough that there is no spillage. This method soothes my OCD!

If you punch a hole in the top of the filter, will that relieve any air-lock and allow the filter to drain more completely? Or is there an anti-drain valve incorporated in the filter?

Thanks

Joined Apr 18, 2020

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204 Posts

Some filters have valves so it might not work. Whatever oil is left between the case and the filter media will remain in the filter, it’s what is left in the center (where the threads are and probably not much) that will drain back down.

Joined Mar 8, 2020

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1,378 Posts

The Anti Drain Back Valve (often abbreviated to ADBV) in the filter will keep the oil in the filter...in the filter when you remove it. This is is the rubber or silicone "flapper" valve that lies just behind all the oil inlet holes around the circumference of the threaded outlet hole. The pressure from the pump moves oil up through those inlet holes, which lifts the ADBV "flapper". When oil pressure is lost (such as when the engine is turned off), gravity and head pressure from the small amount of oil that's still in the filter will push that ADBV "flapper" back down, sealing those inlet holes. At the same time, the large threaded outlet hole will also drain free...as it drains back into the engine's oil galleries down below. All of this happens pretty much "immediately" after you shut the engine off.

The oil filters I've removed (the Subaru factory filter, the visually identical Subaru dealer filter, and aftermarket Fram Tough Guard filters) haven't so much as dripped a single drop when I removed them. I agree with the notion above that these top-mounted filters are laughably easy to change. You could go out to the car dressed in your Sunday best, change the oil filter, and you wouldn't have the slightest sniff of oil on your hands.

Can you replace an oil filter without changing the oil

Joined Mar 25, 2021

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389 Posts

I am taking delivery of my new Ascent today. I intend to follow the break-in procedures, and also change the filter at around 500 miles. My reasoning is that any residual machining swarf will be trapped by the filter, while the oil itself will still be fresh. Just to satisfy my curiosity, I'll cut open the filter and see how much of whatever has been trapped.

I change my first at 500 then 3500.( I'm real worried about new ring wear particles ) then i might go to 4K . There telling me 7500 but I will do one myself in between. Audi went to 12K mile drain intervals which to me is clearly out of bounds. Anyone who does this , if they are leasing it the second owner will have some issues..I personally would not purchase a vehicle with 12K mile pmi's.

Can you replace an oil filter without changing the oil

Joined Sep 19, 2017

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12,947 Posts

It's a top mounted oil filter, so, it's easy enough to remove without draining the sump. If you let the car sit long enough, the filter will be relatively dry, making it painless and clean to swap.

Joined Oct 6, 2018

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372 Posts

Discussion Starter · #13 · 12 mo ago

If you let the car sit long enough, the filter will be relatively dry, making it painless and clean to swap.

This is what I was/am hoping for! haha We rarely drive the car for daily use purposes so it usually does sit a week or more at times.

Do you guys usually just hand tighten the filter or is there a torque spec that needs to be followed? This is the first car I've had since 2013 that doesn't use an element filter so and I've gotten used to torquing the housing to a certain spec.

Can you replace an oil filter without changing the oil

Joined Aug 19, 2018

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3,681 Posts

Can you replace an oil filter without changing the oil

2019 Ascent Touring (CWP)

Joined Aug 16, 2017

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6,047 Posts

There telling me 7500 but I will do one myself in between

If you're talking about your Subaru, the maximum mileage interval is 6000 miles. Always an option to change things sooner, but not a good idea to go beyond.

Can you replace an oil filter without changing the oil

Joined Sep 19, 2017

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12,947 Posts

This is what I was/am hoping for! haha We rarely drive the car for daily use purposes so it usually does sit a week or more at times.

Do you guys usually just hand tighten the filter or is there a torque spec that needs to be followed? This is the first car I've had since 2013 that doesn't use an element filter so and I've gotten used to torquing the housing to a certain spec.

Here's what you need to know...

  • Oil Drain Plug: 41.7 N-m / 4.3 kgf-m / 30.8 ft-lb
  • Oil Filter: 12 N-m / 1.2 kgf-m / 8.9 ft-lb

Can you replace an oil filter without changing the oil

Joined Aug 19, 2018

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3,681 Posts

Here's what you need to know...

  • Oil Drain Plug: 41.7 N-m / 4.3 kgf-m / 30.8 ft-lb
  • Oil Filter: 12 N-m / 1.2 kgf-m / 8.9 ft-lb

Funny how a lubricated drain plug is so hard to remove sometimes when it’s only torqued ~31ft-lb…

My point there was if these specs were always followed you’d never have a stuck or stripped drain plug, rarely have to use anything but your hands to remove the filter.
If you’re mechanically inclined then a torque wrench shouldn’t be required for an oil change, at your own discretion of course. If not, use a torque wrench to save headaches down the road!

Joined Apr 17, 2019

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15 Posts

If you get the chance, install a Fumoto quarter turn vale for draining the oil. It sure makes oil changes easy and cleaner.

Joined Oct 6, 2018

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372 Posts

Discussion Starter · #19 · 12 mo ago

Here's what you need to know...

  • Oil Drain Plug: 41.7 N-m / 4.3 kgf-m / 30.8 ft-lb
  • Oil Filter: 12 N-m / 1.2 kgf-m / 8.9 ft-lb

Thanks! Hand tight it is for the filter since my torque wrench doesn't go that low... haha

Funny how a lubricated drain plug is so hard to remove sometimes when it’s only torqued ~31ft-lb…

My point there was if these specs were always followed you’d never have a stuck or stripped drain plug, rarely have to use anything but your hands to remove the filter.
If you’re mechanically inclined then a torque wrench shouldn’t be required for an oil change, at your own discretion of course. If not, use a torque wrench to save headaches down the road!

I used to just hand tighten my cars with the more "traditional" filters, but got into the habit of following torque specs more recently. Pretty much always followed the torque specs for the oil pan plug though - I know of too many instances of those getting stripped (never personally though)!

Can you replace an oil filter without changing the oil

Joined Sep 19, 2017

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12,947 Posts

Thanks! Hand tight it is for the filter since my torque wrench doesn't go that low... haha

lol, yep, it's a pretty low torque value.

Can you replace just oil filter?

It is, in fact, possible to change the filter alone, with varying degrees of difficulty. The filter is usually installed above the level of the oil pan, so you don't have to worry about all the oil pouring out, but do expect a little.