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21 Sport
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2,225 Posts
Thanks for posting! Great question and I find that these posts are like social experiments... You clearly stated that you weren’t looking for the negative replies, rather looking for advice on how to pre-fill the filter. Yet, so many people could not help but chime in their $0.02🤣
Anyway, I’d be curious to see if you try your way and compare it to the pedal to the medal non ignition recommendation.
and there's always someone to fan the flames. this is the way of the internet
 

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Butchin' Moderator
2018 Orange Subaru Crosstrek Limited
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1,590 Posts
Some wonder if the US will ever inch its way to the only sane system of measurement, the metric system, but I've done the following calculations with the English system.

Using a Wix Filter dimensions correct for a 2018 Subaru Crosstrek. WIX Dimensions given: 3.4" high with a 1.285" radius. Not counting the fillet at the top where the case curves. Gives ~17.64 Cubic Inch Capacity which translates to approximately 9.44 liquid ounces. Since the filter media and inner structure takes up some portion of this space and I'm not willing to rip one apart for science maybe we could grant a rough estimate (I simply pull this figure out of hat as I don't have any basis to make a guess) of 60% of the volume is available for storage of liquid. This would make the liquid volume of a Wix Crosstrek Filter about 6 fluid ounces (~177 mL), or for the chefs in our midst, 12 Tablespoons.

I'm not familiar with the path oil takes in a Subaru but my experience to date is that the oil filter is at the output end of the oil path, there to clean it of course, but the oil is driven from the pump directly through the oil galleries first to vital parts of the engine first. If this is correct I would expect the oil pump to immediately move oil in the pan into the galleries until it couldn't access oil in the pan. If this is correct then I would expect the engine not to run without oil pressure at start up with an empty oil filter as the 6 ounces that need to fill represent a very small percentage of the available quarts stored in the pan. I don't know how many fluid ounces a Subaru oil pump a moves per second.

So, I don't bother to fill the filter as it was entirely too difficult to fill it properly using a winch and jackstands to flip the car over...:)

Whew.
 

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2019 Crosstrek Plug-in Hybrid
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1,132 Posts
Yes it does.Be it turning a key or pushing a button,they are both just a way of completing the circuit to engage the starter.
Curious if the same process works with the hybrid since when I start the car it always starts the EV system and not the engine. Maybe I'll try this in 6 months at my next oil change, but yesterday I did the change and just started the car immediately into charge mode so that the engine actually runs. Figure that was better than not running the engine for a few days.
 

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Butchin' Moderator
2018 Orange Subaru Crosstrek Limited
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1,590 Posts
It seemed like an obvious topic that would have been beaten to death and I did try searching 🤔.

I appreciate the replies and saw the gas pedal topic somewhere else to get oil flow. That sounds easier than my original plan to pull a fuse and get oil flowing.
I still plan prefilling and allowing it to soak in for a while and try a quick flip/spin maneuver with some oil in there 😎.

As an outsider coming into the subaru world I have noticed a common thought(not just here) of ‘if subaru wanted you to do it then it would be in the manual, otherwise it is nothing to worry about’. There is a lot of trust in subaru and their engineers for sure. I was underwhelmed when browsing my manual for basic info on simple things like bulb sizes and often saw a recommendation to just take the car to the dealer rather than providing any info.

Now my next question, what brand oil should I use if I want to gain HP.... joke joke joke 😁
aaaaaarrrrrrrrrrrrggggggggggggggghhhhhhhhhhhhh............ :)
 

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2021 Crosstrek Limited
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717 Posts
It doesn’t matter what is Upstream of the filter but what is Downstream. However since it only takes a “nano second” I guess it doesn’t matter.
Actually, both matter. Both galleys need to be full before oil pressure is built up.

Hmm did not know that. But at the end of the day it is still un necessary but to each his own.
Lots of OBDII cars have this, it's for when the car is flooded, putting the pedal to the floor does not inject fuel.
 

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578 Posts
This being my first ever Vertical oil filter setup on my 21 sport, how does anyone prefill it? Second question, WHY does no one prefill?

On other vehicle forums it is a beaten to death topic that prefill is always recommended. I really do not like the idea of having to circulate oil up into a dry filter, it looks like it would hold maybe 1/3 qt easily, that is a lot of oil. Unless subaru thought about this and it somehow doesn’t oil starve when the filter is dry...? I am rather good at not spilling much on horizontal filters but vertical, can you flip it over fast enough? Maybe half full and fast flip?

I tried searching here but it is one of those hard search terms to get good results.
I know many will chime in and swear by never prefilling and never had problems, that is great, for you. I would like to hear from those that do prefill and any tips / techniques not to make a mess.
In Australia (and Southern Hemisphere) we can pre-fill because we are down under. So it works well as gravity is the opposite way than for you all up North. So the oil stays full in the filter when you turn it over.
 

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2021 Sport 2.5 cvt
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113 Posts
Discussion Starter · #73 ·
In Australia (and Southern Hemisphere) we can pre-fill because we are down under. So it works well as gravity is the opposite way than for you all up North. So the oil stays full in the filter when you turn it over.
Do you have to shop vac the old oil out though? Actually that may not be to bad of a system…
“I’ve been shop vac’ing my oil out for 20 years and never had a problem.”
 
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