High(er) Oil Pressure

[Ragsf15e]

For the last 2-3 years, my oil pressure was 74-76psi and 180-185 degrees in cruise.  I have all the data from my edm930.  Last Thursday I changed the oil (I do the grunt work and my IA spun on the filter and safety wired).  Then on Saturday I flew a 2 hour cross country.  Oil pressure 81psi the whole time, 180 degrees temp.  Huh?  Today I flew home, same thing.  Any reason why it might change a little higher like that?  Obviously it’s still perfectly in the green but it’s definitely different which has made me wonder…

IO-360A1A

Edited April 22 by Ragsf15e

[DCarlton]

If you have all the data…. Curious, did the pressure change at all from when the oil was fresh to when it needed changing ?  

[Ragsf15e]

47 minutes ago, DCarlton said:

If you have all the data…. Curious, did the pressure change at all from when the oil was fresh to when it needed changing ?  

Nope, in the past, oil change hasn’t been noticeable.  I’m not sure this oil change is responsible, but strangely it only started immediately after it.

Oil use is noticeable for me though as the oil “ages”.  I have to add more per hour (slightly) as it gets old. However, the pressure was always the same.

[BDPetersen]

I will watch with interest for answers/theories. After replacing my oil sump gasket a couple years ago I noted an increase in oil pressure (no connection implied). Haven’t figured out a reason or problem.

[PeteMc]

14 hours ago, Ragsf15e said:

Any reason why it might change a little higher like that?

Okay, "eliminating" dumb question round...   With the change in Wx you didn't up the weight of the oil?  By any chance did  you add more oil than normal?

Did you completely fill the oil filter before spinning it on?  If not, here is one I'm just tossing out there as a NON mechanic thinking of what could change the oil pressure.  I've "heard" stories about oil filters coming apart inside if you don't fill them fill them first and then startup the engine.  It sounds a bit far fetched and I'm guessing it is an old hangar tale or it had to do with older style filters on maybe radial engines, but maybe it is true.  If the filter is defective and there are now extra material in the wrong place, might it not change the Oil Pressure indication.  Depending upon where your oil pressure sensor is, it might be backwards and you'd show lower pressure if it was a defective filter.  (Mechanics???) 

And do you just muscle the cowling off/on or do you have something to support it.  I used to do it alone but it was really hard on the edges. 

 

[Ragsf15e]

2 hours ago, PeteMc said:

Okay, "eliminating" dumb question round...   With the change in Wx you didn't up the weight of the oil?  By any chance did  you add more oil than normal?

Did you completely fill the oil filter before spinning it on?  If not, here is one I'm just tossing out there as a NON mechanic thinking of what could change the oil pressure.  I've "heard" stories about oil filters coming apart inside if you don't fill them fill them first and then startup the engine.  It sounds a bit far fetched and I'm guessing it is an old hangar tale or it had to do with older style filters on maybe radial engines, but maybe it is true.  If the filter is defective and there are now extra material in the wrong place, might it not change the Oil Pressure indication.  Depending upon where your oil pressure sensor is, it might be backwards and you'd show lower pressure if it was a defective filter.  (Mechanics???) 

And do you just muscle the cowling off/on or do you have something to support it.  I used to do it alone but it was really hard on the edges. 

 

Same oil (xc20w-50).  No I haven’t ever put oil in my filter first, and I don’t think my IA does either.  Interesting though be supposedly a “blockage” can increase it?

The old models with the aluminum cowl are really easy to get back on by yourself.  Maybe the whole top cowl is 5 pounds?  I’m guessing the fiberglass ones are a little more heavy…

[PeteMc]

57 minutes ago, Ragsf15e said:

Interesting though be supposedly a “blockage” can increase it?

Question for the IA & APs here or to ask your guy.  I really don't know, but if the output was blocked, I'd think there would be higher pressure going in and less coming out.  But again, depends upon where the pump is and where the sensor is.  I'm just thinking about the flow of liquids in general and how you can get different pressures at different points in the same line.  But I don't know anything specific about your engine and how the oil flow. 

And my guess is this shouldn't apply, but there is an adjustment for oil pressure, at least on my engine.  Don't know how it would get changed, but that is one other variable. 

 

[PT20J]

You are still in the normal range, but something is somewhat different. If it were mine, I'd just watch it, and if it doesn't get worse, I'd see what happened after the next filter/oil change. If you are worried about it, you could just change the filter and see if that makes a difference since that is the only part that was changed. 

[EricJ]

I'd tend to agree that unless it does something really outrageous to just keep an eye on it and see what it does after the next oil change.   If it goes back to what it was, ok, if it stays with what it's doing now, maybe that's just the evolution of how the engine behavior is trending.   Engine monitor data and oil analysis may be useful.

 

[PT20J]

One other thought: When was the last time you checked the suction screen in the sump? There might be some carbon in there reducing the flow rate slightly that might have an effect on oil pressure. Draining the oil might have migrated some carbon to the sump where it was picked up in the screen. This is just a spitball thought, though.

[Ragsf15e]

12 hours ago, PT20J said:

One other thought: When was the last time you checked the suction screen in the sump? There might be some carbon in there reducing the flow rate slightly that might have an effect on oil pressure. Draining the oil might have migrated some carbon to the sump where it was picked up in the screen. This is just a spitball thought, though.

I agree with your above to watch and wait.  If it stays the same throughout this oil change, I’ll have my mechanic check the oil screen.  That’s a good idea as he usually needs a little push to do that and I don’t do that myself.

[EricJ]

18 minutes ago, Ragsf15e said:

I agree with your above to watch and wait.  If it stays the same throughout this oil change, I’ll have my mechanic check the oil screen.  That’s a good idea as he usually needs a little push to do that and I don’t do that myself.

They're a pain to get out and put back in in a Mooney.   Worth checking once in a while if there's a potential issue, though.   I don't think a blocked suction screen would increase output pressure, but it's an excuse to take a look.

If there's a new restriction somewhere (slight blockage in an oil passage), the temps are lower than usual (potentially if the vernatherm is behaving a little differently), or the oil thicker than usual (unlikely unless it's colder), or the regulator has changed behavior slightly,  the gauge or transducer has aged a bit, any of those could increase pressure indication a bit.    The temps changing could do it, even from the air through the oil cooler changing a bit for whatever reason.    Since it's a small change it's worth monitoring.

I'm a bit envious of people who have airplanes that behave consistently enough that such a small change is noticeable.   My temps and pressures move around a lot, apparently depending on a lot of different things.   

[Utah20Gflyer]

The simple answer is a hanger fairy dialed up your oil pressure when you weren’t looking.   Normally a hanger fairy would only complete work they knew the owner wanted, but maybe yours went rogue.  

[Ragsf15e]

38 minutes ago, Utah20Gflyer said:

The simple answer is a hanger fairy dialed up your oil pressure when you weren’t looking.   Normally a hanger fairy would only complete work they knew the owner wanted, but maybe yours went rogue.  

I’m just glad he didn’t dial it down!

[M20F]

Grasping at straws but if you used a rag or paper towels to clean off the filter adapter could be something that got left behind.  Could be a clog of some kind in the filter.  
 
I would try changing filter and see if that has an impact, really only thing I can think of. 

[Shadrach]

5lb delta is not a lot. Perhaps this filter has a defect that is causing a slight restriction or the manufacturer has changed the filter media. My guess is that this is filter related. 
I never pre-fill my filters nor do I know anyone who does.

[M20F]

Automotive filter from Reddit probably minimal in aviation but in automotive filters a lot of knock offs.

 

[PeteMc]

3 hours ago, Shadrach said:

I never pre-fill my filters nor do I know anyone who does.

Interesting.  I noticed it at my first oil change when I got my plane and at every shop I've gone to, which just happened to all have been very knowledgeable Mooney shops. 

I'll have to ask what they do at the shop doing my Annual now, which is new to me and NOT a Mooney shop, though in asking around they have a good rep. 

 

[Kelpro999]

Sometimes I’ll tie hoses out of the way for access to whatever, cooler hose perhaps? Or bumped transducer with a wrench? 

[Shadrach]

4 hours ago, PeteMc said:

Interesting.  I noticed it at my first oil change when I got my plane and at every shop I've gone to, which just happened to all have been very knowledgeable Mooney shops. 

I'll have to ask what they do at the shop doing my Annual now, which is new to me and NOT a Mooney shop, though in asking around they have a good rep. 

 

My filter spins onto the rear of the accessory case. Pre-filling it would be about as smart as the clerk at 7-11 pre-filling the Slurpy cups before putting them in the horizontal cup dispenser. I assume that yours is mounted vertically with the open end of the filter facing up?

[vik]

Old oil diluted by gasoline and who knows by what else vs new clean oil. Few psi up sounds pretty normal. I observed similar with the cars if an accurate gauge is installed. Check if the same happened right after previous oil changes if you can identify the dates.

Other theories include a gunk washed out from under the oil pressure relieve valve. 

Best advise is already given - just watch it for now since something changed. Take the action if necessary.

Vik

[skykrawler]

I think prefilling filters is more about reducing the amount of time at engine start to fill the filter with oil and establish pressure to the important bits.  I do it.  Of course, it can't be completely filled without making a mess putting it on.

The OP is quoting numbers that imply high precision like a digital engine monitor.   A change in ground or resistance in the circuit is all it takes to produce a different number.

[Ragsf15e]

2 hours ago, skykrawler said:

I think prefilling filters is more about reducing the amount of time at engine start to fill the filter with oil and establish pressure to the important bits.  I do it.  Of course, it can't be completely filled without making a mess putting it on.

The OP is quoting numbers that imply high precision like a digital engine monitor.   A change in ground or resistance in the circuit is all it takes to produce a different number.

That’s true, but it seems very stable for an electrical “change” to have happened.  I flew it again today and was seeing 80-81 very stable still.  I’m going to download the data and compare it to last time I had the oil changed.  I’ll post that this weekend.

[cbarry]

Assuming the EDM930 oil pressure reads zero when on and the engine is not running?

[EricJ]

18 hours ago, skykrawler said:

I think prefilling filters is more about reducing the amount of time at engine start to fill the filter with oil and establish pressure to the important bits.  I do it.  Of course, it can't be completely filled without making a mess putting it on.

The OP is quoting numbers that imply high precision like a digital engine monitor.   A change in ground or resistance in the circuit is all it takes to produce a different number.

Horizontal-mount filters typically drain into the case when the engine isn't running, so if you fill, or partially fill the filter you may only get the benefit of that if you start the engine fairly quickly after installation.   Takes me longer to get the safety wire on than that probably happens, so I stopped bothering with it.

A vertical mount filter that faces up so it'll hold the oil when not running will benefit from a pre-fill.    There are some Continental engines with the filter vertical facing down, so anything that hasn't drained just makes a mess when you take the filter off.   Can't pre-fill those at all.