oil pressure
10-15-2003, 07:13 PM
#1
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Join Date: Jul 2003
Posts: 90
oil pressure
I just had the oil changed the otherday and put in penzoil 10w-40- as usual but did not add the stp oil additive yet. Without the additive, at lights and stoped the oil pressure will drop ( not dangerously but signifigently ) under acceleration it goes back to normal. But untill the pressure gets back up the car runs like crap, real jerky like. I made sure the shop did it right and filled it up good too. What do you all think?
10-15-2003, 07:38 PM
#2
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Join Date: May 2003
Location: Fort Lewis, Wa
Posts: 56
Ok what do you mean by
But untill the pressure gets back up the car runs like crap, real jerky like.
Are you saying that it doesn't have power, tries to stall, sounds like a midget with a hammer under the hood beating the heck out of everything? Give us a little bit better idea.
Also on the oil pressure. That oil additive makes it more gooy. (for lack of a better word) that means that it won't "wash" back down into your oil pan as easily. If you notice after you run the car, get out and listen to the oil, you can basically hear it returning to the sump. almost sounds like someone is pouring water in there. that is because it is hot. (small science lesson) Hot things become liquid. Hot liquid pours quickly doesn't stay around and chat. When you add an additive it slows the process down and allows the hot liquid to stay around a little bit longer. This is why you see the variance in your pressure. It is changing according to how your engine is running, speed, heat, all that good stuff.
But untill the pressure gets back up the car runs like crap, real jerky like.
Are you saying that it doesn't have power, tries to stall, sounds like a midget with a hammer under the hood beating the heck out of everything? Give us a little bit better idea.
Also on the oil pressure. That oil additive makes it more gooy. (for lack of a better word) that means that it won't "wash" back down into your oil pan as easily. If you notice after you run the car, get out and listen to the oil, you can basically hear it returning to the sump. almost sounds like someone is pouring water in there. that is because it is hot. (small science lesson) Hot things become liquid. Hot liquid pours quickly doesn't stay around and chat. When you add an additive it slows the process down and allows the hot liquid to stay around a little bit longer. This is why you see the variance in your pressure. It is changing according to how your engine is running, speed, heat, all that good stuff.
10-15-2003, 07:57 PM
#4
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Hmmm,
Fishpig, that what I thought was happening.. But Ive never noticed it so dramatically in any other car, besides it seems that the oil woulnd be draining back while the engine is still on. As far as better describing shaky, iam at a loss. There is no sounds or pinging or anthing comming through the hoody. The engine i raising in rpms and speed smoothly. It feels like it surges, and shakes the car - almost like a U-joint going out. I know its not the u-joint however.
Fishpig, that what I thought was happening.. But Ive never noticed it so dramatically in any other car, besides it seems that the oil woulnd be draining back while the engine is still on. As far as better describing shaky, iam at a loss. There is no sounds or pinging or anthing comming through the hoody. The engine i raising in rpms and speed smoothly. It feels like it surges, and shakes the car - almost like a U-joint going out. I know its not the u-joint however.
10-16-2003, 09:15 AM
#5
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Join Date: Mar 2001
Posts: 3,249
2 main things come to mind with low oil pressure. bad sender and/or gage or bad bearings. Make sure the sender is good. This is a common used car lot tactic to make the car sound good. Low oil pressure may mean the lifters cannot get pumped up right and that affects performance. In any case, if I had to resort to this sort of trickery to get the oil pressure up, I have a problem with the engine. I usually use 5W30 except in the winter and then 0W30 and I get the needle about halway or 30 psi warm idle. Usually 33.
10-17-2003, 08:27 PM
#6
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Join Date: Jun 2002
Location: P'COLA, FL
Posts: 463
its all about the wear on the motor, or how "loose" a new one is built.
a chevy only needs 6psi per 1000 rpms.
i have a low 11 second car and i only have 20psi at idle, fully warm, with a high psi pump. shoots to 70psi at the touch of the gas.
the jerky thing you are talking about sounds like the car is idling to low, that will also reduce oil pressure. try changing cap rotor plugs, if you havent. might check the voltage on your tps sensor too, lil things add up.
my .02
a chevy only needs 6psi per 1000 rpms.
i have a low 11 second car and i only have 20psi at idle, fully warm, with a high psi pump. shoots to 70psi at the touch of the gas.
the jerky thing you are talking about sounds like the car is idling to low, that will also reduce oil pressure. try changing cap rotor plugs, if you havent. might check the voltage on your tps sensor too, lil things add up.
my .02
10-17-2003, 08:55 PM
#7
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Join Date: Jul 2003
Posts: 90
Originally posted by 1SLOSBC
its all about the wear on the motor, or how "loose" a new one is built.
a chevy only needs 6psi per 1000 rpms.
i have a low 11 second car and i only have 20psi at idle, fully warm, with a high psi pump. shoots to 70psi at the touch of the gas.
the jerky thing you are talking about sounds like the car is idling to low, that will also reduce oil pressure. try changing cap rotor plugs, if you havent. might check the voltage on your tps sensor too, lil things add up.
my .02
its all about the wear on the motor, or how "loose" a new one is built.
a chevy only needs 6psi per 1000 rpms.
i have a low 11 second car and i only have 20psi at idle, fully warm, with a high psi pump. shoots to 70psi at the touch of the gas.
the jerky thing you are talking about sounds like the car is idling to low, that will also reduce oil pressure. try changing cap rotor plugs, if you havent. might check the voltage on your tps sensor too, lil things add up.
my .02
Thanks interesting, thanks for the input. The TPS sensor is new and okay, the cap and wires are fairly new, but I get some new ones and see how that goes.
10-18-2003, 01:25 PM
#8
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Join Date: Mar 2001
Posts: 3,249
Originally posted by 1SLOSBC
its all about the wear on the motor, or how "loose" a new one is built.
a chevy only needs 6psi per 1000 rpms.
i have a low 11 second car and i only have 20psi at idle, fully warm, with a high psi pump. shoots to 70psi at the touch of the gas.
the jerky thing you are talking about sounds like the car is idling to low, that will also reduce oil pressure. try changing cap rotor plugs, if you havent. might check the voltage on your tps sensor too, lil things add up.
my .02
its all about the wear on the motor, or how "loose" a new one is built.
a chevy only needs 6psi per 1000 rpms.
i have a low 11 second car and i only have 20psi at idle, fully warm, with a high psi pump. shoots to 70psi at the touch of the gas.
the jerky thing you are talking about sounds like the car is idling to low, that will also reduce oil pressure. try changing cap rotor plugs, if you havent. might check the voltage on your tps sensor too, lil things add up.
my .02
6 psi per thousand? Sounds kinda low if it doesn't have a minimum for a street car. I am at 30 psi on an idle and it has an idle of 850. That would mean my pressure is acceptable at 5 psi? For a race motor that might be 0k depending on how it is built. I hit 45 on WOT and 27-30 on idle when the engine is warm. Of course at cold idle it is aroud 45-50 psi
10-18-2003, 02:42 PM
#9
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Join Date: Jul 2003
Posts: 90
Wow, maybe i do not have low pressue. Under acceleration and when cold it is 60psi and when warm at idle will drop to about 30pi - and drop down a bit and back up. I just have noticed a corralation between preformance and smoothness of idle at the high and low pressures.
10-19-2003, 03:17 AM
#11
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Join Date: Feb 1999
Location: Springfield,OH. U.S.A.
Posts: 2,947
I've always believed in the 10psi/1000rpm for a street car, which means at idle 10psi is enough to keep the crank floating. But at 6000rpm / 60psi it has enough pressure to get oil into the tightening clearances of bearings etc.
The type of oil plays a big part in pressure and the same goes for the filter. I've used filters like Duetsch(sp?) which actually lowered my idle pressure by nearly 10psi and a GM truck filter brought it back up.
Pennzoil is a thinner type oil, but I like it b/c it's not a wax base oil, it won't cook down to sludge up my lifter valley and oil drainbacks. And I know from people who've used it long before me it's got an excellent track record.
Our factory Z28 oil pumps are high pressure /regular volume and run between 50-60 cold, 40-50 hot above 2000rpms. Idle oil pressure isn't really important as long as the oil light doesn't come on and it goes up while driving.
Yeah I agree the looser an engine is built or gets due to wear, the lower the idle pressure will get, but oil additives are just "bandaid" symptom fixes. Getting the oil too thick won't let in into the bearings and can wear them faster even with good pressure. The only way to correct the problem is a tighter rebuild, or overhaul. Cam bearings are sometimes the biggest pressure bleeders and are often overlooked.
The type of oil plays a big part in pressure and the same goes for the filter. I've used filters like Duetsch(sp?) which actually lowered my idle pressure by nearly 10psi and a GM truck filter brought it back up.
Pennzoil is a thinner type oil, but I like it b/c it's not a wax base oil, it won't cook down to sludge up my lifter valley and oil drainbacks. And I know from people who've used it long before me it's got an excellent track record.
Our factory Z28 oil pumps are high pressure /regular volume and run between 50-60 cold, 40-50 hot above 2000rpms. Idle oil pressure isn't really important as long as the oil light doesn't come on and it goes up while driving.
Yeah I agree the looser an engine is built or gets due to wear, the lower the idle pressure will get, but oil additives are just "bandaid" symptom fixes. Getting the oil too thick won't let in into the bearings and can wear them faster even with good pressure. The only way to correct the problem is a tighter rebuild, or overhaul. Cam bearings are sometimes the biggest pressure bleeders and are often overlooked.
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