Oil Pressure Interpretation

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I've loved gauges since I was a kid, so naturally I bought one for my car. Just one. I chose a digital oil pressure gauge. I heard this is a good thing to be able to monitor, kind of like a vital for the engine the way I see it. So back in December I installed the gauge sender with a sandwich adapter between the filter and the oil cooler and wired the gauge in the interior and it works great. I am happy with my gauge, but I would just like to learn more about what I can learn by observing it.
The car: 2007 Honda Civic Si (K20Z3)
The Oil: Amsoil AZO 0W-30
The gauge reads:
Cold Idle: ~95-105psi
Cold 3000rpm: 115+psi (only did that once cold)
Warm Idle: ~19-26psi
Warm 3000rpm: ~88-95psi
Warm 8000rpm: ~105-108psi (hard to look at while driving)
I was torn between buying an oil pressure or oil temperature gauge and I chose pressure because I believed that pressure gave a better indication of the overall "health" of the engine and could warn of a failure/problem in the oiling system. I also believed that the pressure would change according to the temperature of the oil so that the pressure gauge was sort of a ballpark temp gauge as well. I was later told, "Stop trying to extrapolate oil temp, because it's not going to be accurate and it's just not an important thing to know in your situation." I trust this guy's opinion, so I really don't know what to think. Ans also, how come I can drive around for an hour and watch the idle pressure at red lights and it reads 21-26psi, but after the first redline run it dips to 18 or 19 psi? Am I getting the oil that hot with just one run through a few gears?
 
Originally Posted By: Guitarman200806
I've loved gauges since I was a kid...

Perhaps it's time to monitor its oil temperature, too?
 
This is the Si model with the k20z3. It's a 2.0L inline four that makes 200hp (at 7800rpm) and fuel cuts above 8000rpm so it's just a high-strung engine. I've established my readings are normal and healthy. The economy minded cars spec a 20wt but the Si specs a 30wt oil.
Honda says minimum spec is 10psi at idle and 44psi at 3000rpm without load, measured at an operating temp of 176 degrees F.
 
Well see that's my problem. I don't wanna drive "easier" I wanna drive it the way I always do, HARD. I also wanna keep things in check while I do that.
 
Those numbers seem WAY high. I'd be interested to see if their is an oil port on a different part of the engine than using the sandwich style adapter.
 
You don't state the model of the gauge or sender. Cheapo or a good one? I've never been fond of digital here. An old school VDO or similar might be substituted to compare readings.

Readings seem consistently high.
 
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Originally Posted By: bubbatime
Those numbers seem WAY high. I'd be interested to see if their is an oil port on a different part of the engine than using the sandwich style adapter.


Agree, I would have thought the oil pressure relief valve would have gone into by-pass mode at about 100 psi.
Maybe you should check your digital gauge against a screw in annolog

Oil temp will give you a good idea when your oil and engine are at full operating temperature. My guess is, it will take far longer than you thought!

15-20 minutes of normal driving.
 
Sorry. The gauge was expensive. It's an AEM 150psi digital unit model number 30-4407. It is very sensitive and will jump between 75-95psi while cruising (normal according to AEM). On my Miata I installed a good old mechanical gauge using an actual nylon oil line from the block into the cabin. I like it more than the digital unit. These numbers don't seem high compared to other k20 engines i've seen, it's normal according to what I read as well. The car is always warmed up well before anything above 3000rpm is reached and my UOA are always great no matter what I throw at this car (drag strip, autox, etc.).
 
Normal Coolant temperature and heat saturating the engine to optimal operating temperature are two different things.
 
I don't understand that one expat. I always warm my car up gently. It's almost to the point where people say I drive too "slowly" for the first ten minutes. I even listen for the thermostat to click to gauge coolant temps reaching op temp.
 
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Oil Temps (that relate to the general temperature of your engine block) tend to LAG coolant Temps. (that are mostly influenced by cylinder head temperature)

In my car, that has both coolant and oil temp gauges, it can often be 10 or so minutes after coolant temps reach normal readings, before oil temps reach the 175 f nominal range.

During this warm up phase, I would imagine you could expect higher levels of wear. So I tend to take it easy.
 
I agree 100%. Coolant temp is definitely not an indicator of overall engine temp. This is why I don't agree with people who start driving aggressively after only a couple minutes of driving. Especially with today's "estimate" temp gauges that aren't actually linear in regard to the temperature.

I guess I'll just buy an oil temp gauge as well to accompany my pressure gauge. I always take more time than everyone else to warm up my car because I believe it's important, but I usually miss out on opportunities for fun by doing so. At least I can prove my point with this thread.
 
If you do, try to get the sender located in the oil pan.

This is the most used location, and the best to give you an average temp, rather than a false reading, too hot or too cool.
 
From Honda FSM page 2-8 for 2007 and Si (K20Z3) engine:

Relief valve oil pressure with oil temp at 176F:

At idle 10 psi minimum

At 3000 rpm 44 psi minimum (FWIW - R18 1.8 engine is 50 psi)

No other oil pressure specs given but FSM has excellent info and diagnostics.
 
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Right. I am aware of those specs as I own the FSM for this car (car is completely self-maintained). Those are just minimum specs from Honda. I have never seen a running k-series with numbers that low. Those are just a borderline to normal numbers.
This morning I drove around nice and easy for 30 minutes then really got on it.
On the 90k mile k20 with ~4k miles on this oil:
Cold idle ~92psi (car idles around 2000rpm for a minute or two)
Warm idle ~21psi
Warm 3000rpm ~88psi
Warm 8000rpm ~102psi (Highest pressure of the trip)
I guess I answered my own question. The indicated 21psi warm idle is usually the lowest the pressure will go with normal driving so that's probably an indication of op temp for oil. But with a/c on or a few redline runs here in Florida, pressure has gone as low as 16psi, only to climb back up to ~20psi with some easy driving mixed in after. Maybe the stock oil-to-water heat exchanger doing its job slowly?
 
Glad you have to FSM - Honda's are among the best written and will become extinct - on line only.

Why not post all this in a Honda forum? Sure to be some sharp owners there.

I still think your readings are high.
 
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I did post it in the 8th civic forum, but most members don't have an oil pressure gauge. I was also told that if I wanted to monitor oil temp, I should have bought an oil temp gauge. I really only want one gauge, so I bought pressure thinking I could ballpark reaching operating temp by just observing the gauge to establish norms. Now everyone thinks I'm crazy. And regarding the readings being high, other forums say high pressure is healthy for these cars. ~100psi is very normal at WOT. It's why members of 8th civic recommended the 150psi gauge instead of 100.
 
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