first off i hope im in the right section. ok so a few months ago or maybe last month but i whatever i left a thread concerning my oil pressure gauge. well im going to bring the question up again because that gauge is really annoying me and i need some clarification. the question is "what is the right reading for the oil pressure gauge at an idle and what is it suppose to read going about 65 mph"? at an idle mine reads between 40 and 60 and going about 65 it reads just a little above 60. also sometimes it will get close to 80 but goes back down to just above 65. you guy think some thinks wrong or im just chewing on my leg for no reason?

 

At most, it sounds like your OPSU might be a little flakey.

 

what weight oil are you using ?

 

in general for 5w-30 to 15w-40 weight oil, you will have between 40-60 psi at idle which is 800-1200 rpm when cold. Cold I would say is when the oil temperature is 70 F or less which will be whenever you start the car when it's cold. The colder it is outside, the higher the oil pressure is likely to be at idle when you first start the car. As the oil gets warmer the oil pressure will drop, and when the oil is colder the oil pressure will be higher. When the engine is hot with oil temperature 200F or more, it is normal to have down to 20psi oil pressure at 800-1200 rpm especially with a 5w-30 motor oil. With a heavier weight oil such as 10w-40 or 15w-40 you be more likely to have 40 psi at 800-1200 rpm. If you're running a 20w-50 oil and you have 20-30 psi at idle when hot then you probably got some bearing wear and excessive clearance.
Oil pressure rises with engine rpm, not vehicle speed. For 65mph if you have an auto I'm guessing around 1800 rpm. I have an M6 and at 65mph if I'm in 6th I'm 1500 rpm which is almost idle. At 2000 rpm you should see a significant jump in oil pressure when hot, such as if you're at 20psi at 800 rpm then you rev the engine to 2000 rpm you should see around 40psi. If the gauge only climbs slightly to like 30psi at most then if the oil isn't super hot you probably have some bearing wear. When the oil temp is not hot, say 150F and lower and you romp on it and get rpms up to 3000-4000 it is normal to get 60-70 psi oil pressure especially with a 10w-40 or 15w-40 oil, the oil pump is pumping and you don't have excessive bearing clearances and you have good oil pressure. The oil pressure relief valve which is on the oil pump opens at 70 psi so you will not get higher oil pressure than that on the gauge unless that relief valve fails and sticks closed but that is very unlikely since the pressure always forces it open. The opposite can happen, although it's not likely, for the relief valve to not fully close so at low rpms oil is flowing out the relief valve when it shouldn't resulting in low oil pressure. Also know that oil temperature lags behind coolant temperature as the engine warms up, and if it's 30-40F outside it will lag behind significantly. You can drive 10-20 minutes with the engine fully warm at 190F and have the oil temperature only 100-140F. If you haven't figured it out yet oil pressure is directly related to oil temperature, because the oil's viscosity changes with temperature.

 

ok so the oil i use is mobile 1 synthetic 5-30. When the cars cold and i start it the oil pressure is just above 60 psi and the when it gets warm that when its between 40 and 60. so what should i do to fix this? and what happens to the motor if the oil pressure i high?

 

If you are concerned a bit, get a manual oil pressure gauge for a more accurate reading.


Also, is you engine all stock?

 

The factory oil pressure gauge is crap..if you want to know what your oil pressure really is get a after market gauge and you will be much happier...same with the engine coolant gauge it is a too...get yourself a dual gauge A piller mount and install those two real gauges and you will be good to go......the manual guages will be a little more of a pain in azz to install because of the oil line that will have to be hooked up to the oil pressure guage .... the electric ones a just as good if you buy a quality product.

 

you don't need to fix anything, your oil pressure is fine!

like i said, the oil pump relief valve is set to open at 70 psi so you would not see over 70-80 psi on the oil pressure gauge unless that fails.

But to answer your question if you really did have high oil pressure which would have to result in the oil pump relief valve staying closed, and high pressure would be over 100psi, then you might see signs of the oil filter bulging outward from the pressure or the o-ring gasket there might start seeping if the filter wasn't real tight. the worst case is the oil filter bursts, which would then cause an immediate loss of oil pressure and you would have major engine damage in about 5 seconds. I think K&N posts burst pressure ratings for their filters, I think most all filters are rated to 150 or 200 psi. The other thing that can happen with high oil pressure is lifter pump up (will only happen on engines with hydraulic lifters which you have) and that can prevent the valves from closing fully and will cause the engine to stumble, backfire, and/or lose power.

 

Is there any thing I can do bring the oil pressure back down? The oil pressure has been doing this for about 5 months now. Also, your right the oil pressure never get to 80 psi, even when I'm flooring it, it gets between 70 psi and 80 psi. I just concern for my car, I want to keep it in good shape.

 

Even if it sat at 80 psi 100% of the time, it wouldn't hurt anything. But, for your peace of mind you might put a real gauge on it and see what it reads. If it's different from the one in your dash, then replace the sending unit.
The only way to know for sure if you even have a problem is to get a real gauge on it as step one.