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Discussion Starter · #1 · (Edited)
Hello!

I've just changed my oil (to Castrol Magnatec 5w30 A5) and noticed the oil pressure gauge reading lower than normal on hot idle - it's exactly halfway between 0 and the first mark, while it used to be halfway between that point and the first mark. I have made almost no miles so far (literally 15 or so). The oil level is just fine (3/4ths of the checked area on the dipstick).

Beforehand I've had some issues with the car - first it was overfilled with oil by a quart, I've drained it and took it to a shop where they determined compression to just perfect, changed the timing chain and the main pulley (?). They however didn't install the intake PCV tube properly, which I mended myself about 250 miles later.

What could be the reason for the low oil pressure? What should my next steps be?

EDIT - updating with my findings for anyone who has this question later on.
  • If you try to compare the oil pressure needle position with pics found on web, take a picture instead of trusting your own eyes. The camera distorts and the pressure looks to be higher in pictures than it does in person
  • Despite multiple threads on the internet, the pressure should not drop with an oil change, I think people were overly vigiliant after they had their oil change. Not a bad thing though!
  • The pressure gauge is calculated based on oil pressure switch, engine speed data and engine head temperature sensor (as opposed to the coolant sensor)
  • When the car is fully warmed up, the pressure gauge should be exactly 1/8th of the way (halfway between 0 and the first tick mark) - common internet knowledge says it should be just below the first mark or even around the middle of the gauge, which is 100% untrue.
 

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If you're taking about 1/4 of the way up the gauge I think that's normal.

Mine is the same way.
 

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Discussion Starter · #5 ·
I don't think that's abnormal. It can get pretty low on hot idle. What's your ambient temp outside? Also - when you say overfilled by a quart - it was at 6.7Q?
Roughly 20 degrees celsius. Actually it was 6 liters, so 6.34 quart, but I'm unsure how much was leftover in the car at the time of pouring.
 

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2014 ST3. Garrett GTX2860R Gen 2. FBO
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Mk3 doesn't have an oil pressure sensor, only an oil pressure switch to trigger a warning light if your pressure is actually low. The oil pressure gauge up in the pod is run strictly off of a pre-calculated value based on temperature and rpm and off of no actual real time information.
 

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Discussion Starter · #10 ·
If you aren't leaking oil presently, I don't think the low oil pressure is a concern based on just the gauge. If you drive the car, does the guage move?
Yes, it does. It is lower than before though. I've made a post on my local ST / RS group and people's pressure on hot idle is higher too, like mine used to be (just before the 1/4 mark, not exactly 1/8th of the gauge).
 

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Discussion Starter · #12 ·
Mk3 doesn't have an oil pressure sensor, only an oil pressure switch to trigger a warning light if your pressure is actually low. The oil pressure gauge up in the pod is run strictly off of a pre-calculated value based on temperature and rpm and off of no actual real time information.
I do realise the service manual explicitly states this (calculation based on coolant temp, oil switch and engine speed data), but I know for a fact my pressure is lower than it was earlier, some people state they see a difference after an oil change too. Those two bits of info just don't check out, period. I'm also seeing it's a bit lower than it should be based on photos of oil pressure from my local ST/RS FB group, this forum and even a Google Image lookup of the aux gauges.

Also consider Ford makes factual errors in their manuals. The pre-2015 Focus ST supplement states a wrong max oil level and the very same service manual that gives info on the oil pressure gauge also refers to the intake MAP as a MAF.
 

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The only way you know is if you removed the pressure switch (connected only to the red warning Light in the cluster) and threaded in an actual oil pressure gauge. Please tell us what the pressures were at specific oil temperature and RPM and monday when i get back to work i can see if Alldata has an oil pressure chart.

Again. The gauge in the pod on top of your dash is purely cosmetic.
 

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Discussion Starter · #14 ·
Please tell us what the pressures were at specific oil temperature and RPM and monday when i get back to work i can see if Alldata has an oil pressure chart.

Again. The gauge in the pod on top of your dash is purely cosmetic.
That would be absolutely fantastic! What do you think should my check points regarding temp and RPM be? I already made a garage appointment, but for next Monday sadly
 

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I will get back to you on temp and RPM based on what the chart says. Sometimes manufacturers will just list one or two pressures in relation to RPM and are vague about the engine being "up to operating temperature". I'll set myself a reminder and see what i can dig up.
 

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Oh and also for clarity-oil temperature is also a calculation and has no actual basis either. The only real fluid temperature sensor on this vehicle is the coolant temp. Everything revolves around that.
 

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Discussion Starter · #18 ·
Ah well, will check based on this anyway and update here, thanks! I've also a bit of a hard time finding pics of the gauges when the car is FULLY warmed up (oil temp points fully up), so if anyone can provide one, I'd appreciate it as well.
 

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Ah well, will check based on this anyway and update here, thanks! I've also a bit of a hard time finding pics of the gauges when the car is FULLY warmed up (oil temp points fully up), so if anyone can provide one, I'd appreciate it as well.
Here's my pic from today. Fully warmed on way to work, drove for about 30 minutes. 75F ambient outside, oil was changed about 500 miles ago with normal Motorcraft 5W-30 synthetic blend. Idle is about where it usually is, on hot days, slightly lower.
 

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Discussion Starter · #20 ·
Here's my pic from today. Fully warmed on way to work, drove for about 30 minutes. 75F ambient outside, oil was changed about 500 miles ago with normal Motorcraft 5W-30 synthetic blend. Idle is about where it usually is, on hot days, slightly lower.
Thanks man I'm getting the car out of the garage today to take a look at the oil filter, I'll be sure to take a look at the pressure at this oil temp you've got (y)
 
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