mouldie Posted October 1, 2014 Share Posted October 1, 2014 Apologies if this has already been covered, I have tried a search but it doesn't give me an exact answer! I'm hoping someone with some technical/theoretical knowledge can educate me please! I'm wondering what creates oil pressure in the engine and whether this is a mechanical component such as a pump or simply the movement of the engine parts? To what extent should oil level affect oil pressure? The reason I ask is that I recently topped my oil level up and noticed that the oil pressure average rose by about 10psi. Should that happen? The pressure range seems to be between 30-90psi with the car sitting at 30psi at tick over, 60psi cruising at 60mph/2,000rpm and never going above 90 between 3-6,000rpm. If oil is getting past the piston rings will that be reflected in oil pressure and can a compression test result be related to oil pressure? Finally, assuming the pressure is proportional to oil level......what happens if you over fill the oil level and how quickly does it go bang (if that's what happens?) Thanks in advance if you've read this far! Quote Link to comment Share on other sites More sharing options...
ATTAK Z Posted October 1, 2014 Share Posted October 1, 2014 Your pressures sound spot on Oil level does affect oil pressure ... at the limit, no oil, no pressure Quote Link to comment Share on other sites More sharing options...
mouldie Posted October 1, 2014 Author Share Posted October 1, 2014 Thanks. Can it be used as a measure of engine health? Quote Link to comment Share on other sites More sharing options...
Keyser Posted October 1, 2014 Share Posted October 1, 2014 Thanks. Can it be used as a measure of engine health? Not really - low oil pressure can be - Thin oil - change it Blocked filter - change it weak oil pump - change it (nightmare job) High oil pressure can be - thick oil (as in sludge) change it Wrong oil type - change it Cold oil - warm car up good pump - smile in contentment However you can have great oil pressure when only running on 5 cylinders and you rings could be gone - this will mean the oil pressure will drop when you burn enough off. ALWAYS CHECK YOUR OIL As Attak said, no oil = no pressure but its usually to late when the red light comes on! 2 Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted October 1, 2014 Share Posted October 1, 2014 Apologies if this has already been covered, I have tried a search but it doesn't give me an exact answer! I'm hoping someone with some technical/theoretical knowledge can educate me please! I'm wondering what creates oil pressure in the engine and whether this is a mechanical component such as a pump or simply the movement of the engine parts? To what extent should oil level affect oil pressure? The reason I ask is that I recently topped my oil level up and noticed that the oil pressure average rose by about 10psi. Should that happen? The pressure range seems to be between 30-90psi with the car sitting at 30psi at tick over, 60psi cruising at 60mph/2,000rpm and never going above 90 between 3-6,000rpm. If oil is getting past the piston rings will that be reflected in oil pressure and can a compression test result be related to oil pressure? Finally, assuming the pressure is proportional to oil level......what happens if you over fill the oil level and how quickly does it go bang (if that's what happens?) Thanks in advance if you've read this far! Oil pressure is purely a result of mechanical movement of the oil pump and maintained by this and regulated from over pressure by the oil pressure relief valve, Oil pressure can be affected by low oil level causing cavitation (air voids in the flow) thick or thin oil will also reduce or increase the pressure, also blocked or obstructed oil filter or oil passages within the engine. Also oil pressure is affected by temperature, despite oil being multi-grade cold oil pressure will be considerably higher than hot oil pressure for the same RPM. With relation to oil pressure being an indication of engine condition, well if the engine has a lot of miles on it or has not been serviced regularly things like bearing clearances and oil pump wear are an indication of condition but not always given the factors mentioned above, it will not however indicate piston ring bore wear. And finally if you over fill with oil depending on amount, slight overfill should be OK but a little more and you could see oil getting past oil seals, and in extreme cases forcing them out of position, but a serious overfill and we are talking 2-3 lt or more cold result in serious mechanical damage. As said your pressure sounds fine. 2 Quote Link to comment Share on other sites More sharing options...
Richf Posted October 2, 2014 Share Posted October 2, 2014 Oil pumps don't create pressure they create flow , resistance to that flow creates pressure Just like when you put your finger over the end of a hosepipe. 1 Quote Link to comment Share on other sites More sharing options...
codders Posted October 2, 2014 Share Posted October 2, 2014 My 04 starts at ~70 psi and then goes down to ~10 (no aircon) or ~15 (aircon). Can easily get to 60 psi average revs. Hard/high revs max 75 psi. Oil level 1mm below H. Do I have an issue? Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted October 2, 2014 Share Posted October 2, 2014 Oil pumps don't create pressure they create flow , resistance to that flow creates pressure Just like when you put your finger over the end of a hosepipe. Chicken...egg! Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted October 2, 2014 Share Posted October 2, 2014 My 04 starts at ~70 psi and then goes down to ~10 (no aircon) or ~15 (aircon). Can easily get to 60 psi average revs. Hard/high revs max 75 psi. Oil level 1mm below H. Do I have an issue? What oil grade are you using? and whats the mileage of the engine? Quote Link to comment Share on other sites More sharing options...
codders Posted October 2, 2014 Share Posted October 2, 2014 My 04 starts at ~70 psi and then goes down to ~10 (no aircon) or ~15 (aircon). Can easily get to 60 psi average revs. Hard/high revs max 75 psi. Oil level 1mm below H. Do I have an issue? What oil grade are you using? and whats the mileage of the engine? 5w30 Mobil 1 and 40k Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted October 2, 2014 Share Posted October 2, 2014 I wouldn't say you necessarily have a problem, although 10PSI is a little low at idle, and personally I would prefer/expect to See 15 to 25 psi, but it could easily be a dodgy sender, presumably the 10PSI is at hot idle? Quote Link to comment Share on other sites More sharing options...
codders Posted October 2, 2014 Share Posted October 2, 2014 I wouldn't say you necessarily have a problem, although 10PSI is a little low at idle, and personally I would prefer/expect to See 15 to 25 psi, but it could easily be a dodgy sender, presumably the 10PSI is at hot idle? Indeed. Do you know how much a sender is? If it's cheap (I already know it's easy to replace) then I'll give that a go. Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted October 2, 2014 Share Posted October 2, 2014 Afraid not, but I'm sure one of the traders here can supply one at a sensible price. Quote Link to comment Share on other sites More sharing options...
GIXXERUK Posted October 2, 2014 Share Posted October 2, 2014 I wouldn't say you necessarily have a problem, although 10PSI is a little low at idle, and personally I would prefer/expect to See 15 to 25 psi, but it could easily be a dodgy sender, presumably the 10PSI is at hot idle? Indeed. Do you know how much a sender is? If it's cheap (I already know it's easy to replace) then I'll give that a go. http://www.clarkmotorsport.co.uk/parts/Oil-Pressure-Switch/25070-CD00A Quote Link to comment Share on other sites More sharing options...
codders Posted October 2, 2014 Share Posted October 2, 2014 I wouldn't say you necessarily have a problem, although 10PSI is a little low at idle, and personally I would prefer/expect to See 15 to 25 psi, but it could easily be a dodgy sender, presumably the 10PSI is at hot idle? Indeed. Do you know how much a sender is? If it's cheap (I already know it's easy to replace) then I'll give that a go. http://www.clarkmoto...tch/25070-CD00A Ouch. Think I'll put a pressure gauge on the car and prove it's the sender first. Thanks Quote Link to comment Share on other sites More sharing options...
GIXXERUK Posted October 2, 2014 Share Posted October 2, 2014 I wouldn't say you necessarily have a problem, although 10PSI is a little low at idle, and personally I would prefer/expect to See 15 to 25 psi, but it could easily be a dodgy sender, presumably the 10PSI is at hot idle? Indeed. Do you know how much a sender is? If it's cheap (I already know it's easy to replace) then I'll give that a go. http://www.clarkmoto...tch/25070-CD00A Ouch. Think I'll put a pressure gauge on the car and prove it's the sender first. Thanks I expected half that price tbh Quote Link to comment Share on other sites More sharing options...
glrnet Posted October 2, 2014 Share Posted October 2, 2014 http://www.ebay.co.uk/itm/Oil-Pressure-SENSOR-Sender-Switch-FITS-SENTRA-ALTIMA-PATHFINDER-XTERRA-350Z-/161425475843?pt=Motors_Car_Truck_Parts_Accessories&hash=item2595b54903 1 Quote Link to comment Share on other sites More sharing options...
comrade Posted October 2, 2014 Share Posted October 2, 2014 Mine idles at 15psi when hot with new Motul 5w30 and HKS oil filter. Before the change it was 25psi with 10w40 and standard filter. I don't see lower idle pressure as a problem, if it is normal under higher revs. As it was said before, pressure does not equal flow and it is the flow that is important, not the pressure in itself. Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted October 2, 2014 Share Posted October 2, 2014 (edited) Mine idles at 15psi when hot with new Motul 5w30 and HKS oil filter. Before the change it was 25psi with 10w40 and standard filter. I don't see lower idle pressure as a problem, if it is normal under higher revs. As it was said before, pressure does not equal flow and it is the flow that is important, not the pressure in itself. Incorrect! restriction is necessary to make sure the oil pressure can be forced between the bearing surfaces when under considerable load of a running engine, why do you think that a good indication of badly worn bearings is low oil pressure. Oil flow on its own would be useless, its the oil galleries and bearings that provide the restriction. Your pressure dropped because of a slight change in oil viscosity from 10 w40 to 5w30. Edited just to keep somebody happy! Edited October 2, 2014 by Tricky-Ricky 1 Quote Link to comment Share on other sites More sharing options...
Ekona Posted October 2, 2014 Share Posted October 2, 2014 The w belongs to the first number, not the second. Quote Link to comment Share on other sites More sharing options...
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