Oil pressure mystery
Discussion
I know there is a lot of discussion here about oil pressure, but can anyone enlighten me on this:
Where is the oil pressure reading taken from, and is the sensor prone to clogging up?
This is my problem: My pressure was a bit lower than many figures posted here, typically 40-50psi on start-up, so I changed the pressure relief spring and gained 10 psi or so. I then had the car serviced and upon collection, I fired it up to see 80psi, the highest I have ever seen.
Since then, however, It has slowly fallen back to pre-pressure relief spring change figures, and when on hot idle is lower than ever. I keep oil topped up to the max line.
My thoughts are that it could have been over filled at the service, perhaps, leading to a high pressure, or that the oil is thinner than the previous stuff (it was the first service for me, so I am not sure what was in there before) leading to the lower hot ide. Of course, the pressure gauge could be on the way out as I can often get an extra 10psi by tapping the glass! Is there an way of verifying pressure with an alternative device of some sort?
The way the pressure readings tailed off over time and jumped back up at service, only to tail off again suggest to me that something is gradually clogging up.
Jon H
Where is the oil pressure reading taken from, and is the sensor prone to clogging up?
This is my problem: My pressure was a bit lower than many figures posted here, typically 40-50psi on start-up, so I changed the pressure relief spring and gained 10 psi or so. I then had the car serviced and upon collection, I fired it up to see 80psi, the highest I have ever seen.
Since then, however, It has slowly fallen back to pre-pressure relief spring change figures, and when on hot idle is lower than ever. I keep oil topped up to the max line.
My thoughts are that it could have been over filled at the service, perhaps, leading to a high pressure, or that the oil is thinner than the previous stuff (it was the first service for me, so I am not sure what was in there before) leading to the lower hot ide. Of course, the pressure gauge could be on the way out as I can often get an extra 10psi by tapping the glass! Is there an way of verifying pressure with an alternative device of some sort?
The way the pressure readings tailed off over time and jumped back up at service, only to tail off again suggest to me that something is gradually clogging up.
Jon H
Jon,
How long is it since the car was serviced? (this will determine the amount of time it took for the reading to deteriorate)
What oil was used at the service?
Does the car use much oil?
Sounds like your guage may be faulty, so probably worth changing to remove it from the equation?
What are your readings under the following criteria:
Start up at idle?
Normal driving under load (approx)?
At idle aftyer the car is fully warmed up and has been driven 5-10 miles?
At idle after the car has fully warmed up and has maybe had a bit of very heavy right foot?
Jules.
How long is it since the car was serviced? (this will determine the amount of time it took for the reading to deteriorate)
What oil was used at the service?
Does the car use much oil?
Sounds like your guage may be faulty, so probably worth changing to remove it from the equation?
What are your readings under the following criteria:
Start up at idle?
Normal driving under load (approx)?
At idle aftyer the car is fully warmed up and has been driven 5-10 miles?
At idle after the car has fully warmed up and has maybe had a bit of very heavy right foot?
Jules.
Jules, answers in bold:
How long is it since the car was serviced? (this will determine the amount of time it took for the reading to deteriorate)
Approx 1000 miles ago, end of May
What oil was used at the service? 0w 40 I believe, will double check on monday
Does the car use much oil? less than 1 litre in last 1000 miles
Sounds like your guage may be faulty, so probably worth changing to remove it from the equation?
What are your readings under the following criteria:
Start up at idle? 45-50psi
Normal driving under load (approx)? 30psi
At idle aftyer the car is fully warmed up and has been driven 5-10 miles? 20 psi
At idle after the car has fully warmed up and has maybe had a bit of very heavy right foot? just under 20psi
Just took it out to verify figures...it is running like a peach at the moment!
Jon
How long is it since the car was serviced? (this will determine the amount of time it took for the reading to deteriorate)
Approx 1000 miles ago, end of May
What oil was used at the service? 0w 40 I believe, will double check on monday
Does the car use much oil? less than 1 litre in last 1000 miles
Sounds like your guage may be faulty, so probably worth changing to remove it from the equation?
What are your readings under the following criteria:
Start up at idle? 45-50psi
Normal driving under load (approx)? 30psi
At idle aftyer the car is fully warmed up and has been driven 5-10 miles? 20 psi
At idle after the car has fully warmed up and has maybe had a bit of very heavy right foot? just under 20psi
Just took it out to verify figures...it is running like a peach at the moment!
Jon
jon h said:
Jules, answers in bold:
How long is it since the car was serviced? (this will determine the amount of time it took for the reading to deteriorate)
Approx 1000 miles ago, end of May
What oil was used at the service? 0w 40 I believe, will double check on monday
IMO 0W-40 is too thin for the Cerb, especially after 20k miles or so, a change to a different grade will see an improvement in oil pressure, I use Silkolene Pro 10W-50 in my Cerb, although currently have Mobil 1 motorsport 15W-50 as it was a freebie. Changing to either of these grades will see a increase in both cold and hot idle pressures.
Does the car use much oil? less than 1 litre in last 1000 miles
Not overly excessive and depends on how the car is driven, some cars endured hard driving and regular track days and still will use less than 1 litre per 1k miles.
Sounds like your guage may be faulty, so probably worth changing to remove it from the equation?
Would still recommend this as it sounds like it may be reading 10psi below what it should, combine this with the recommended grades of oil and you should having almost normal oil pressure again.
What are your readings under the following criteria:
Start up at idle? 45-50psi
Normal
Normal driving under load (approx)? 30psi
I meant when applying the throttle during normal driving so would expect this to be 50+psi?
At idle after the car is fully warmed up and has been driven 5-10 miles? 20 psi
Does appear a little low
At idle after the car has fully warmed up and has maybe had a bit of very heavy right foot? just under 20psi
As above
Just took it out to verify figures...it is running like a peach at the moment!
Jon
How long is it since the car was serviced? (this will determine the amount of time it took for the reading to deteriorate)
Approx 1000 miles ago, end of May
What oil was used at the service? 0w 40 I believe, will double check on monday
IMO 0W-40 is too thin for the Cerb, especially after 20k miles or so, a change to a different grade will see an improvement in oil pressure, I use Silkolene Pro 10W-50 in my Cerb, although currently have Mobil 1 motorsport 15W-50 as it was a freebie. Changing to either of these grades will see a increase in both cold and hot idle pressures.
Does the car use much oil? less than 1 litre in last 1000 miles
Not overly excessive and depends on how the car is driven, some cars endured hard driving and regular track days and still will use less than 1 litre per 1k miles.
Sounds like your guage may be faulty, so probably worth changing to remove it from the equation?
Would still recommend this as it sounds like it may be reading 10psi below what it should, combine this with the recommended grades of oil and you should having almost normal oil pressure again.
What are your readings under the following criteria:
Start up at idle? 45-50psi
Normal
Normal driving under load (approx)? 30psi
I meant when applying the throttle during normal driving so would expect this to be 50+psi?
At idle after the car is fully warmed up and has been driven 5-10 miles? 20 psi
Does appear a little low
At idle after the car has fully warmed up and has maybe had a bit of very heavy right foot? just under 20psi
As above
Just took it out to verify figures...it is running like a peach at the moment!
Jon
Easy cure could be different grade of oil and change the oil pressure guage, if not then more investigation may be needed.
Jules.
Actually... I have been pondering the whole issue of oil pressure and wonder if some of the accepted wisdom is correct.
If, for example you consider my situation where the main issue is low pressure when hot, one of the oft quoted remedies here is to go to a thicker oil, but does this actually help? Sure, the reading on the dial may be better, but is there actually better flow of oil around the engine, which is what is surely the most important issue.
Consider, if you will, a Macdonalds thick shake (stay with me on this one...!) compared with a similar cup/straw combination with, say, Coke in it. In my mind, the Coke represents 0w40 versus the 15w50 race spec thick shake. Now, it takes a lot more pressure (suck, in this case) to get the thick shake up the straw due to the higher viscosity, but in a given time, there will be a lot less flow than for the same effort sucking on the coke. Pressure, after all, is a measure of resistance, is it not? And surely we need flow around the engine, not resistance to flow, i.e. pressure. Does this make sense, or am I talking complete bollox?
Jon
If, for example you consider my situation where the main issue is low pressure when hot, one of the oft quoted remedies here is to go to a thicker oil, but does this actually help? Sure, the reading on the dial may be better, but is there actually better flow of oil around the engine, which is what is surely the most important issue.
Consider, if you will, a Macdonalds thick shake (stay with me on this one...!) compared with a similar cup/straw combination with, say, Coke in it. In my mind, the Coke represents 0w40 versus the 15w50 race spec thick shake. Now, it takes a lot more pressure (suck, in this case) to get the thick shake up the straw due to the higher viscosity, but in a given time, there will be a lot less flow than for the same effort sucking on the coke. Pressure, after all, is a measure of resistance, is it not? And surely we need flow around the engine, not resistance to flow, i.e. pressure. Does this make sense, or am I talking complete bollox?
Jon
jon h said:
Actually... I have been pondering the whole issue of oil pressure and wonder if some of the accepted wisdom is correct.
If, for example you consider my situation where the main issue is low pressure when hot, one of the oft quoted remedies here is to go to a thicker oil, but does this actually help? Sure, the reading on the dial may be better, but is there actually better flow of oil around the engine, which is what is surely the most important issue.
Consider, if you will, a Macdonalds thick shake (stay with me on this one...!) compared with a similar cup/straw combination with, say, Coke in it. In my mind, the Coke represents 0w40 versus the 15w50 race spec thick shake. Now, it takes a lot more pressure (suck, in this case) to get the thick shake up the straw due to the higher viscosity, but in a given time, there will be a lot less flow than for the same effort sucking on the coke. Pressure, after all, is a measure of resistance, is it not? And surely we need flow around the engine, not resistance to flow, i.e. pressure. Does this make sense, or am I talking complete bollox?
Jon
Sense. But someone who knows will come along and say you`re missing the point or something.If, for example you consider my situation where the main issue is low pressure when hot, one of the oft quoted remedies here is to go to a thicker oil, but does this actually help? Sure, the reading on the dial may be better, but is there actually better flow of oil around the engine, which is what is surely the most important issue.
Consider, if you will, a Macdonalds thick shake (stay with me on this one...!) compared with a similar cup/straw combination with, say, Coke in it. In my mind, the Coke represents 0w40 versus the 15w50 race spec thick shake. Now, it takes a lot more pressure (suck, in this case) to get the thick shake up the straw due to the higher viscosity, but in a given time, there will be a lot less flow than for the same effort sucking on the coke. Pressure, after all, is a measure of resistance, is it not? And surely we need flow around the engine, not resistance to flow, i.e. pressure. Does this make sense, or am I talking complete bollox?
Jon
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