Ok, so I changed my oil the other day, and now the pressure is lower. On Wed, before I changed it and was running erronds, it read as always. 60psi at speed, and about15psi at idle. That night after I changed the oil and filter, it reads 30psi at speed and 15 at idle. So what gives? I changed from some unknow filter (automac #1151) to the nippon ones that the RX7 store sells. Oil is pensoil 10w-30. I know that my gauge isn't the most accurate, its the dash gauge, but what could cause it to drop like that????

 

u probably were running 20w-50 before and changed to 10w-30 which is thinner oil thus producing less pressure in oil. also with 10w-30 u will discover any oil leaks in ur engine (ask me how i know :-p)

 

You spilled oil on the oil pressure sensor under the oil filter pedestal?


-Ted

 

You know I'm not real sure about this one. I was pretty careful, but **** happens right. I'm curious how this would change the pressure levels only at speed though. Actually I'm curious how this would change anything.

As far as the oil grade. I'm not sure what viscosity(sp?) was used before, I didn't change it myself last time, and I'm pretty sure I didn't specify to the shop that did what I wanted. I'm pretty sure that IF i told them i told them 10w30 as that is what i have been using in my other rex for years.

I'm going to try to figure out how to put a manual gauge directly on the sender so I can see what the actual pressure reading is. This is mainly out of curiosity now.

 

Some filters cause lower oil pressure.

 

The oil and filter are not the direct cause. They make too small of a difference. It's either a gauge problem or mechanical problem that needs fixing. If it's a mechanical problem, 20w50 is thicker so it'll leak slower, etc. It won't solve the problem, but it'll slow it down til you fix it.

I'd verify the reading with an external gauge (buy/borrow/etc.). If your pressure really does drop below 30psi, I wouldn't drive until you fix it. Low oil pressure leads to a spun bearing b/c you need that pressure to keep the bearing from directly touching the surface it's supporting. That'll take an engine rebuild to fix. 15-30psi might still be enough (maybe someone who knows more can chime in), but I wouldn't chance it. If your pressure reads fine with the external gauge, then you know it's a gauge problem.

 

weird my car read 30 psi at idle and would up to like 40psi at speed. i use castrol 10-30 though

 

W the thing is though it reads lower now then it did befor the change so that is only like 4 hours time difference. There is no way that the gauge is going to change that quickly. (unless Ted is right about the spilling, get back to me Ted)

I realize that my gauge may be off, but as long as it is consistantly off in that four hour period, then changing the oil and filter is what is causing the drop.

If i check it, and the mechanical gauge reads the same readings, then AGAIN why did it drop.

I cant check it today though, i gota get a root canal.

As far as the oil filter changing the pressure or the oil viscosity changing the pressure that does make sense. But what does that mean for the actual pressure of the system? Is it better to make fair presseure at with a thin oil, or make good pressure withe a thicker oil?

 

It might "make sense" but I didn't find it to be true.
When I switched from 20w/50 to 10w/30 (upon my mechanic's recommendation) the readings on my two gauges (stock cluster and SPI aftermarket) did NOT change significantly.

The gauges have been checked against a mechanical gauge screwed into the stock sender location.

 

well, I guess that leaves the filter
problem is, nippon is supposed to be the OEM ofr mazda

the number on the filter is B6Y2-14-302, if anyone has an OEM filter let me know if this matches.

 

Check the oil presure sender unit. Make sure electronically its clean and secure and also check to make sure its screwed in tight into the block. Make sure the oil filter is no leaking.

I heard a few times that 10 psi for every 1000rpm is what you want. So according to that he shouldn't go above 3000rpm?

 

You partly misunderstand on the mechanical side. The oil & filter didn't cause the problem directly. But the oil might have revealed/magnified a pre-existing problem. i.e., thinner oil finds leaks more easily.

 

Mine is marked: B6Y1 14 302 9A.
I have no idea what that means...

 

Who ever told you that is talking out their ***.

 

^ Hopefully a known engine rebuilder can verify this instead of someone with 208 posts

 

OK so I finally got my test gauge in place. Removing the pressure sending unit is a pain in the ***. So my test gauge reads alot better. after warmup the car reads about 65 PSI at 3k rpm idle is at about 20ish. That pretty much tells me that my sensor unit is off. I'm going to order a new one in a few. I realize that my readings are still a bit low, but im not nearly as worried about it now.

That being said.

What was it that caused the drop to begin with? In other words which should I change out first to test it? I'm leaning to the oil, maybe it had 20-50 in it. Any more ideas would be great.

thanks

Aug

 

crap gota wait till late next week for the sensor.

 

[QUOTE=ericgrau;7299686]I'd verify the reading with an external gauge (buy/borrow/etc.). If your pressure really does drop below 30psi, I wouldn't drive until you fix it.QUOTE]

30psi is quite a bit of pounds per sq inch. I mean tires have 30 psi in them and they keep your rims off the road.(sorry stupid analogy but true)

I've been running with about 10psi at idle for a while now actually put 4K miles on the motor(not easy miles either). But I have jetted the eccentric shaft. As I understand 20psi at idle is more than enough pressure for Idle, but near 3K rpm you want to be at or above 60.

Personally I wouldn't be too concerned with with it. If it were less, like 30psi at 3k I'd worry, or almost 0 at idle could be a problem.

So your probably seeing the 20psi at Idle because your pressure regulators are probably gettin a little unsprung/old and the lighter wieght oil. If you at 60 at 3k your safe.

 

Ted's probably right. He was a wealth of information when I had my last car and I'm sure hes only gotten better.

 

If the answer wasn't obvious, spilling oil on electronic contacts is bad.
The oil pressure sensor is right under the oil filter pedestal, and oil filter changes can easily drip oil right on top of the sensor.
The connection isn't fully covered, so getting oil on the contacts will affect oil pressure signal to the gauge.

A quick squirt with some brake cleaner should reveal if this is the problem.


-Ted

 

The oil pressure supports a bearing. If the pressure gets too low, you could get a spun bearing. Spun bearing = rebuild time. PSI is pounds per square inch. Tires have a lot of square inches. Bearings don't. 4k miles might not be long enough to tell before the bearing gets worn to nothing, especially if 10psi is enough to kinda sorta support it. I dunno, if it were me I might drive far enough to get to auto service places, but I wouldn't chance it for too long.

Anyway the O.P. should at least try what RETed said first. Not like it's hard. Most of the time bad oil pressure is just a gauge/sensor issue. Maybe the O.P. can borrow an external gauge too, or see if someone will check it for him real quick.

 

Sorry Ted, it wasn't obvious at first. But as soon as I got under there to test my pressure it was. Gunk everywhere. Definatly going to clean it befor re-install.

 

OK an update.

I finally got the part, but I had to wait another week to get it in. (damn work) The gauge works now. Its no longer off by about 15 psi. Matches up pretty close to the mech gauge I had in there.

Just for ***** and giggles I swapped the filter out for a stock Mazda one. Made no difference compared to the "Nippon" one. I'm going to try 20w-50 the next change I make and see how that changes things.

 

could spilt oil cause HIGH oil pressure readings?

 

well i have a problem wit mine now when i turn my car on it skips up to just under 120 then when its warm it skips back dwn to just under 60 but when i dive it it starts skipin back up when i accel. when i deaccel. it goes back dwn to just under 60 someone please help send me a message or suttin