80psi to much oil pressure?

Messages
38
Location
N.C
In my 1994 Grand Cherokee(5.2moparV8)i switched form castrol Gtx 10-30 to Mobil delvac 15-40. the motor has 150K on it. With castrol it has about 35psi at hot idel(600rpm) and 65psi cold ideal but now with Mobil it has over 80psi cold and 45psi hot idel the cold pressure seems really high to me and will that cause any damage. Like oil starvation due to less flow? [I dont know] but it consumes almost no oil.
 
Messages
3,542
Location
Colorado
Your oil pressure guage might not be accurate. I had a 1989 GMC and at hot idle the guage said 5psi and any gas it went up past 80psi!! The guage was not working right. I was told 80 psi is to high but that could be on that perticuler engine.
 
Messages
5,112
Location
Airlie Beach Australia
Hi, it all depends on the engine and its design parameters - you need to check the "normal" pressure for yours Some relief valves operate at up to 9bar+ ( about 135psi) and the idle oil pressure is not a good indicator of the engine's health Most engine makers have a strict protocol about oil pressure measurement ( engine oil type, temperature, rpm and etc. ) Regards
 
Messages
2,602
Location
The Tropics of Antartica
quote:
Originally posted by bugman53: In my 1994 Grand Cherokee(5.2moparV8)i switched form castrol Gtx 10-30 to Mobil delvac 15-40. the motor has 150K on it. With castrol it has about 35psi at hot idel(600rpm) and 65psi cold ideal but now with Mobil it has over 80psi cold and 45psi hot idel the cold pressure seems really high to me and will that cause any damage. Like oil starvation due to less flow? [I dont know] but it consumes almost no oil.
My opinion is using a thicker oil like that will prematurely wear out the oil pump over time . If it's over 80lbs now at cold idle thats more than the engine needs when warm at wide open throttle . My last race motor made 31 lbs at over 8k rpm with 40wt and lived a long life .No idle though cause pressure was near zero . There is alot to viscosity choices and hydraulic lifters as well . The makers made choices for the owners since many don't fully understand the effects . For more info search Rhoades Lifters . They are a hi bleed lifter very tempermental to vi . If your having consumption problems I would suggest one of the better HM oils available in a 10w-30 wt . Castrol and Pennzoil are but two of these type products that are actually designed for higher mile engines like yours . I really think you will benefit more from a hi-mileage oil than that diesel oil your using now . But you will have to try it and decide for yourself . A little more money than a tractor oil but hey , what did that last tank of gas cost ya ? [Smile]
 
Messages
3,858
Location
Cape Cod, MA
Since discovering that Ford, in its infinite wisdom, put a fake oil pressure gauge in the Marauder, quite a few members of mercurymarauder.net have replaced the factory gauge with a real, working, one. We all have almost identical pressure readings (100 lbs cold, 50 lbs at a steady 40 MPH (warm) and 25 lbs idling in gear (warm)), so I have to assume that they're normal... [ March 03, 2004, 08:22 AM: Message edited by: RF Overlord ]
 
Messages
13,132
Location
By Detroit
quote:
Originally posted by bugman53: In my 1994 Grand Cherokee(5.2moparV8)i switched form castrol Gtx 10-30 to Mobil delvac 15-40. the motor has 150K on it. With castrol it has about 35psi at hot idel(600rpm) and 65psi cold ideal but now with Mobil it has over 80psi cold and 45psi hot idel the cold pressure seems really high to me and will that cause any damage. Like oil starvation due to less flow? [I dont know] but it consumes almost no oil.
What is the hot oil pressure with each of these oils? The critical number usually hot (and I mean after a good 15 mile run) at highway speed, maybe around 2000 or 2500 rpm. You service manual can tell you the spec. For example, my pickup ('95 F150 300 I6) specs 40-60 psi hot at 2000 rpm. I was getting 35 with 5w30 and now am happy running 10w40 and getting 45 psi. In your case, given the idle pressure, I strongly suspect that you should stick with a 10w30 (presuming the gauge is good). If in doubt about the gauge the shop can hook up a precision test gauge, but again it has to be hot. You will know when it is hot as the pressure will slowly come down from the cold pressure as you drive and then will stabilize after 10 to 15 miles. But 80 cold is not necessarily too high as my motorhome runs 75 cold and then around 58 hot at 2000 rpm. Get the spec pressure and check the 15w40, you may be OK, but if too high, I would drop back to 10w30. Why did you stop using 10w30, using oil? Are you burning it? Maybe a different 10w30 will result in less consumption. [ March 03, 2004, 09:11 AM: Message edited by: TallPaul ]
 
Messages
2,602
Location
The Tropics of Antartica
I think those 4.6 motor use a gerotor style pump . They are OHC and with cold pressure like that it would be scary to even entertain the idea of using a tractor oil in them vs the OHV topic motor . The pump might be bypassing even at cold idle with 5w-20 . I'm curious as to the bypass specs of the 4.6 oil pump . Anyone have that information ?
 
Messages
13,132
Location
By Detroit
quote:
Originally posted by Gary Allan: Something doesn't seem right here. ... I would think that if you saw a peak pressure of 65 with one oil ...you would see 65 with any oil cold ...
Excellent point. When I ran 5w30 in my pickup and then switched to 10w40 the cold pressure was the same for both, but the hot pressures changed. The oil pump pressure relief valve is the limiting factor, unless the thinner oil just could not get enough pressure to open the pump relief valve; then you would see a difference. He needs to look not only at the hot cruise speed pressure, but also find out what the pump (not filter) relief valve pressure is supposed to be. [ March 03, 2004, 01:08 PM: Message edited by: TallPaul ]
 
Messages
9,448
Location
USA
You are fine. If the pressure goes to high (unlikely) then the bypass will open. Cold PSI reading does not count for anything. In order for an oil pressure reading to valid it must be done with the oil at operateing temps and the rpm setting recomended by the OEM. The 10 extra psi hot is nothing to worry about. It is actualy a good thing. DOdge sells 15W50 Mobile for use in the Viper. The Vipers engine is based on your engine with 2 extra cylinders. My DOdge had a different engine but it ran at 100 psi above idle with 10W30 with hot oil!
 
Messages
9,448
Location
USA
If the engine was haveing starvation problems you would know it quickly. You water temps would sky rockets, the oi ltemp light would light, your valve train would be makeing really eerie noises, power would be down drasticly as well. AN oil starved engine is not a happen sounding engine. If you decide to change the oil out of concern then please save a sample and send it off for UOA!!! I would love to see the UOA. I am betting all is well but I am not a Ford Modular Man. Consult a service manual it should give bypass pressure and what rpm the oil pressure should be checked at. Usualy any pressure hot that is below bypass pressure is great! Alot of systems are 100PSI systems! 65PSI Hot is fairly common hot above 1800 RPMs! The old rule of thumb was 25-45 PSI at idle with 10 PSI per 1000 RPM's for optimum engine life. THe way a bypass is designed when you go into bypass it just bleeds off escessive pressue. Normaly if the bypas is stuck open you get low pressure that does not change with RPM. [ March 03, 2004, 11:23 PM: Message edited by: JohnBrowning ]
 

bugman53

Thread starter
Messages
38
Location
N.C
Thanks for all the replies. I just put in a new oil pressure sender so I know that’s good. With the miles I thought a thinker oil would be good b\c of the tolerances opening up. But It makes sense that the pressure would be the same, but if its not going to hurt anything than im just going to leave it. BTW would sludge cause this? Maybe a restricted oil passage before the oil relief valve its letting the pressure build up?
 

bugman53

Thread starter
Messages
38
Location
N.C
I changed from 10w-30 Because I’ve read so much about the use of diesel oil to help keep a motor clean(pretty bad sludge)but with 10W-30 the oil pressure would read around 70-75 peak(around 2,500 and leveled off)so I guess the peak pressure is not any higher its just reaching it at a lower RPM. And I checked the with JEEP and they say 10-80psi normal so I guess im alright. BTW I was in a rush to change the oil(b\c I put on a new intake manifold and got a little coolant in the oil) and it was a Sunday and the only place open was walmart so I had to get a fram filter(Let the flames begin )But I got the X2 so could that have caused the differences in the pressure,. It had a napa gold before.
 
Messages
39,805
Location
Pottstown, PA
Something doesn't seem right here. Your oil pump should be moving the exact same volume with either oil. I would think that if you saw a peak pressure of 65 with one oil ...you would see 65 with any oil cold ..with the exception that you may exceed 65 briefly as you can overwelm the pressure relief slightly in sub freezing start up as you increase the rpms. Again this is only for a few minutes. (I'm trying to express this and am failing miserably) Let's say the old oil has a lower viscosity - okay ..but that would STILL make the SAME pressure at a higher volume as the Delvac would at cold idle or at a lower rpm. The hot idle and cruise pressure may change ..but the peak cold ..assuming that you drive it when it's still cold ..I wouldn't think that there would be any difference at all (except for maybe two minutes in sub-freezing temps). Damage? In reality I think that you are just spending a few pennies more in the energy to pump the stuff through the engine. Your distributor shaft is taking the strain of it. In extreme cases it it usually the bottom of the distributor that wears out (the keyed/splined/hexed end of the shaft) ...but I've only seen this happen once in over 30 years ...and then it had nothing to do with oil selection.
 
Messages
16,004
Location
NE,Ohio
quote:
Originally posted by Motorbike:
quote:
Originally posted by bugman53: In my 1994 Grand Cherokee(5.2moparV8)i switched form castrol Gtx 10-30 to Mobil delvac 15-40. the motor has 150K on it. With castrol it has about 35psi at hot idel(600rpm) and 65psi cold ideal but now with Mobil it has over 80psi cold and 45psi hot idel the cold pressure seems really high to me and will that cause any damage. Like oil starvation due to less flow? [I dont know] but it consumes almost no oil.
My opinion is using a thicker oil like that will prematurely wear out the oil pump over time . If it's over 80lbs now at cold idle thats more than the engine needs when warm at wide open throttle . My last race motor made 31 lbs at over 8k rpm with 40wt and lived a long life .No idle though cause pressure was near zero . There is alot to viscosity choices and hydraulic lifters as well . The makers made choices for the owners since many don't fully understand the effects . For more info search Rhoades Lifters . They are a hi bleed lifter very tempermental to vi . If your having consumption problems I would suggest one of the better HM oils available in a 10w-30 wt . Castrol and Pennzoil are but two of these type products that are actually designed for higher mile engines like yours . I really think you will benefit more from a hi-mileage oil than that diesel oil your using now . But you will have to try it and decide for yourself . A little more money than a tractor oil but hey , what did that last tank of gas cost ya ? [Smile]

Keywords.. YOUR OPINION [Smile] I think you are reading to much into this. 15w40 is not any thicker than 10w40 when hot... its not some magical goop you run only in diesel engines..... Its just OIL. Rand
 
Messages
2,569
Location
College Dorm...
quote:
Originally posted by Rand: Keywords.. YOUR OPINION [Smile] I think you are reading to much into this. 15w40 is not any thicker than 10w40 when hot... its not some magical goop you run only in diesel engines..... Its just OIL. Rand
Actually, Rand, you're statement isn't exactly true. HDEO 15w-40's are traditionally forumlated thicker than PCEO 10w-40's, and thus are a tad-bit thicker at operational temps. I do agree with you that there is a common misconception that HDEO's are ONLY for diesel engines...obviously, they are not, and are a great oil to run in gas engines as well. In regards to this engine, I believe Delvac 1300S is an exceptional oil that will work great in this application...it's not too "thick" and will not cause oil starvation. Before "freaking out", make sure the factory gauge is working properly and is accurate. BTW, go ahead and change out the Fram and put the Napa gold back on. Besides the fact that it is a better filter, it will give you a reference point to refer to in comparison to the oil you ran beforehand.
 
Top