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Old 05-26-2009, 08:30 PM   #1
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Default Low oil pressure...

I know this type of question has been asked a million times, but i must bring this up again or i will never know if i have a serious problem or not.


So here is the problem. My set up ishttps://www.miataturbo.net/forum/newthread.php?do=newthread&f=9 in my sig.
I have a crappy NAPA oil filter and 5-30w oil in the engine. The car does not smoke excessively and i just did a compression test which came out as follows: 1-190psi 2-190psi 3-170psi 4-190psi.

Wet test brought the compression in number 3 to 190 so its the rings are not doing to well.

But above is not the problem i am having. The problem is with oil pressure. When i drive the car nice and dont redline it the pressure seems to be normal at idle its right between zero and 30 and at cruising its between 30 and 50. However when i redline the car a couple times or just drive it hard for even a short time my oil pressure goes as low as just a few millimeters from 0 and when cruising its just under 30.

The car runs fine and no different from usual when the pressure is lower, i have enough oil and no oil leaks.

The only thing that i think might be causing this is that the oil is to light and after i drive the car hard it heats up more and the oil becomes really liquid like.

Any ideas? Any one experienced this?

Cross posting with M.net to get more insight into this.


Thanks in advance.
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Old 05-26-2009, 08:40 PM   #2
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I can't really say why, but my car does this as well. I am running a proper JDM filter and Synthetic 5W-50 so I wouldn't expect the filter or oil to have much effect. My guess has always been the decreased viscosity from the higher oil temps combined with higher clearances from the higher temperatures. I also don't trust the stock oil pressure gauge much, it could just by some hysteresis effect on the sensor.

Only other thing I could think of would be that the oil pressure under high RMP gets up enough to open the bypass valve, and once opened it leaks until everything cools down and it sits back in better.
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Old 05-26-2009, 08:48 PM   #3
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Originally Posted by matttheniceguy View Post
I can't really say why, but my car does this as well. I am running a proper JDM filter and Synthetic 5W-50 so I wouldn't expect the filter or oil to have much effect. My guess has always been the decreased viscosity from the higher oil temps combined with higher clearances from the higher temperatures. I also don't trust the stock oil pressure gauge much, it could just by some hysteresis effect on the sensor.

Only other thing I could think of would be that the oil pressure under high RMP gets up enough to open the bypass valve, and once opened it leaks until everything cools down and it sits back in better.
I think this could be what is going on. Is there a way to check that?
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Old 05-28-2009, 10:15 AM   #4
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Same thing happened to mine, ran halfway between 0 and 30 under load while running Mobile1 5w30 synthetic. Did an oil change to 10w30 Mobile1 Synthetic, including filter and it now sits above 35psi. Just an FYI.

Also, I can't find the diagram, but someone did some research and found the Supertech 6607 filters, found at Walmart, are equivalent to filters that come stock on the car. I've had no problems to date.

Oh yeah, and check your coolant temps, I was running pretty hot, that can add more wear on your engine, especially in the hot July season. Check your temps this weekend, especially when it's going to be 75+.
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Old 05-28-2009, 12:19 PM   #5
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Thats good to know that you had the same problem. Btw, i will need your advice on engine building pretty soon here. I did check my coolant temps a few times when the weather was really hot and it usualy is at 196-204. 196 is when i cruise and 204 is when i beat on it hard.
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Old 05-28-2009, 01:04 PM   #6
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Quote:
Originally Posted by matttheniceguy View Post
I can't really say why, but my car does this as well. I am running a proper JDM filter and Synthetic
wtf are you talking about? jdm oil filter? are you serious?
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Old 05-28-2009, 04:50 PM   #7
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Quote:
Originally Posted by disturbedfan121 View Post
wtf are you talking about? jdm oil filter? are you serious?
My first reaction as well...I can only hope this reference is to the Mazda filter.
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Old 05-29-2009, 07:00 PM   #8
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Originally Posted by gospeed81 View Post
My first reaction as well...I can only hope this reference is to the Mazda filter.
Sorry, forgetting you guys get real Mazda filters down in the US.

Mazda Canada sources their oil filters domestically (as far as I know they are a FRAM filter). If you were to go into a Mazda dealership here and buy a filter for your car, you will get one that dramatically restricts oil flow and creates a noticable drop in oil pressure. Miata shops up here provide a solution by just ordering proper filters for the car from Japan. It sounds a bit extreme, but they only end up costing $6 cdn or something like that, and you get a proper filter for the car that doesn't kill your oil pressure.
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Old 05-30-2009, 12:17 AM   #9
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Yikes... a few mm from 0psi? That's dangerous. Is your gauge not fucked up somehow? Maybe have a buddy jiggle the wires while the motor's running to check if the sender's good. Otherwise, it sounds like something might be fubar'd with your oil pump's pressure relief valve. Getting to it would be a pain.

Just FYI, I don't think this will completely fix your problem, but you can try using a Purolator PL14610. It's used on the Mazda V6's, so you get ~1" extra length and less pressure loss across the filter. I gained about 10psi with the extra flow. I also upped my oil viscosity to 10W40 when I went turbo. That helps with hot pressure loss.
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Old 05-30-2009, 12:36 AM   #10
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i bet my problem is connected with too light of an oil. And this only happens when i drive the car hard.
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Old 09-17-2009, 11:27 PM   #11
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bumping this thread instead of making another one. I have another problem. I think i am paranoid but still.

For some reason now my oil pressure is high. hot idle is at 35-40psi when driving at 3k the pressure is close to 60, when acceleration hard it goes over 60psi.

I changed to 5w30 oil and the pressure staid the same but now i got nasty oil smell when i come up to a stop and its not even burn oil smell its more of a raw oil smell. So i decided to go back to thicker oil and dumped the just changed 5w30 to 10w40 oil. The smell is still there, maybe not as strong but still there and the oil pressure is still too hight.

Any ideas?

I did clean the connector on the oil pressure sender. I am running Napa gold filter. Tomorrow i am going to try and put K&N or some other better filter and see if it helps.
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Old 09-17-2009, 11:59 PM   #12
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Oil filters shouldn't make that big of deal. It's good to hear you're on 10w40 now, more of us have experience with that. I see highish numbers (45 I think?) with a cold start up, and any blip of the throttle spikes the gauge. It should obviously be lower when "hot", by how much I'm not terribly sure, its been a while. Your numbers sound good though.
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Old 09-18-2009, 12:41 AM   #13
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my cold start is sometimes as high as 60 psi and blips peg it at 90.
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