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Hey everyone got an oil pressure question. My cars been at the shop cause of high oil pressure issues. Just grasping at straws trying to figure out what’s going on or if it’s something obvious just haven’t thought about. New shortblock, heads, turbo, cam gears. OP readings are being taken from front oil galley above pump where the low OP warning sensor sits. It’s around 25 with a mechanical OP test gauge at idle. Tested gauge on another car and read normal so gauge works. From what I read in FSM idle should be 14 psi? Shop would like it around 18....seems low to me but I’m a noob to turbo Subaru’s. I also read should be 10psi for every 1k rpm. No banjo bolt filters, clean passages, oem oil pump. Any ideas? Bearing clearances too tight? Thanks in advance.
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Thanks for the reply. That’s kind of what I’ve found...that seems to be the consensus on NASOIC too with the WRX/STI motors. AFAIK it’s running 5W30 Subaru Dino oil....I was going to switch to T6 or AMSOil 5W40. I figured 22 was ok...14 is pretty low and 18 isn’t much better. I’d rather have at least 20 so there’s flow.
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I see the 14psi in the FSM, but also notice that's at 600rpm which is below idle RPMs

Mine is higher than 43psi at 5k rpm, but I'm also running a heavier 5w40 oil that may be contributing to it.

 

Side note: just realized that the oil pressure light switch only triggers at 2.5psi or below... Seems to be a little too late...

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As a comparison, mine runs about 20psi at idle warm and 80psi at 3k rpm and above with 5w30.

FSM for the 2009 legacy/outback says 14psi or more at 600rpm, and 43psi or more at 5k rpm. Kinda hard to get a feel for what may be abnormally high with those specs.

 

I have often wondered if my pressure was higher than most, especially at startup. Looks like my operating temp pressures are somewhat normal, but at start up I can see as high as 92psi at idle. Never had an issue though. Always comes down to 20psi once warm. I thought it might have been the prosport sending unit, but I had checked it with another brand and had similar pressures. Sensor mounted off tee at oem pressure switch above oil pump using a remote sensor locator kit for what it's worth.

 

At 2.5 psi I think you have already damaged quite a bit especially at highway rpms.

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Thanks for the reply, I did some math and based on 14psi at 600, if you take that and move it up proportionately to 800-900 rpm it’s right around 20/21 psi, which makes sense...ya the stock low oil pressure sensor is pretty worthless. Longacre racing makes an adjustable one...I think from 15-50 psi. Thought about putting that one in the back oil galley since my OP gauge will use the front oil valley. But with a 15psi low OP light at least you’ve got more of a fighting chance than at 2.5psi. My 85 S10 is the same way...uses high mileage 10w30 but it’s pretty high until it gets warm, then it drops to around half (can’t remember exact #s), it’s the 2.8 v6. I’d feel better with 20~psi at idle and then 80 at 3k rpm....that way it’s flowing and doing what it’s supposed to...
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I will look into the Longacre product you described. Sounds like cheap insurance. Thanks for the idea.

I mounted my oil pressure gauge above the oil pump to have a good idea of oil pump health as well as pressure and use the rear oil galley plug for my oil temp sensor. I don't like the idea of filter sandwich blocks.

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Here’s a link: http://www.longacreracing.com/products.aspx?itemid=1734&prodid=7451&pagetitle=Gagelites-Warning-Light-Kit---15-50-psi-Oil-Pressure-1%2f8%22-NPT

Bought something similar (20 psi pressure warning sensor) and was going to tie it to a relay to cut ignition power...but that’s on a 350 sbc with carb and HEI dist on my other project car (street/strip/corner carving)...little different than a LGT. Hope that helps people with an alternative to the stock low OP sensor issue. Y’a not crazy about sandwich adapters...almost bought one but glad I did some more research first.

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http://www.longacreracing.com/products.aspx?prodid=7462

I think I will try this one. Cuts off at 12 psi. I am going to have to get inventive mounting it as it looks bigger than the oem and I would like to keep it in the stock(ish) location.

I added the oil pressure gauge because this is the first vehicle I have ever owned that didn't have a factory gauge.

Off topic, I too am familiar with v8's. I have 2 mid 80's c10s and an 02 suburban. All are in varying stages of use or builds. This is my first Subaru but 2nd in the family. My wife has a 2015 outback.

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  • 1 year later...

Additional info here-

When I swapped to a BNR 16g, i found tons of oil goop in the intake manifold and throttle body. The cartridge seals had blownout. While I was replumbing the new oil feed lines to the 16g, I double checked the banjo bolt filters that I was told were removed. I found one at the oil feed line to the turbo, which was half clogged. Obviously i removed it. I ran the turbo oil feed from the galley plug at the front of the motor using a combination of ATP lines and earls -4 AN fittings. Now my oil pressure is about 75psi at start up and 20psi at idle with a cruise of 70 psi.

Hope this helps somebody.

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