Lower oil pressure

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Sep 17, 2011 | 10:03 PM

abrahamkay

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Lower oil pressure

I recently just switched to a full synthetic oil from regular oil. I have noticed that when the oil is cold that it has the same oil pressure the regular oil had (around 75 psi for both cold), but when the full syn gets to operating temps the oil pressure is way below (around 60) what it was when the regular oil (around 75) was at operating temp. Is this normal? Is it because I am using a different weight of oil to? I broke the engine in with Valvoline 50W, and used Valvoline 20W50 till about 850 miles ago when I switched to the Valvoline Full Synthectic 5W30.

Sep 18, 2011 | 06:16 AM

Luke1996ta

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From: ottawa ohio

never should of switched

Sep 18, 2011 | 06:50 AM

davidws6

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5W30 is a little thin but 60psi of pressure is good.

Mine runs about 60 > 65 with 15/50 Mobil 1 warmed up above idle.
Idle is about 35 > 40 with a Melling Hi volume pump.

Sep 18, 2011 | 07:44 AM

Darkman

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The proper oil viscosity is not determined by maximizing hot oil pressure. If that were the case higher viscosity would always win regardless of the internal lubricating/cooling requirements.

Unless you have deviated from OEM main bearing clearances, the appropriate viscosity is in the vicinity of 0W-30, 5W-30, or 10W-30 for the street. Higher viscosities may be appropriate for sustained high speed running, such as road racing where heat (measured in terms of oil temperature) and fuel dilution are a factor.

Sep 18, 2011 | 08:09 PM

abrahamkay

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I have Clevette 77 race bearings in the engine. I don't know if the bearing clearances have changed. The engine builder didn't tell me anything on that when I ordered the engine.

Sep 18, 2011 | 08:20 PM

s346k

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From: johnson co.

there is a huge difference between 20w50 and 5w30, the drop in pressure is directly related to the use of thinner oil.

Sep 18, 2011 | 08:35 PM

camaroz28lt1at

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From: Savannah, GA

^^^Yup, what he said...

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Sep 19, 2011 | 06:28 AM

Darkman

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From: Spring, Texas

Quote:

Originally Posted by abrahamkay

I know that there is a huge difference from the 20W50 and 5W30. I was asking bout the pressure being lower cause of it being Full Syn.

The short answer is no (it is not due to one being synthetic). The full answer is not quite that simply because you can have two synthetic oils, both within the same 5W-30 category, and within the range for 30 weight oil, that are nonetheless not identical in terms of specific viscosity. But if you have a petroleum-based oil and a synthetic oil that both have identical viscosities - they will result in the same oil pressure in the same engine.

Finally, I would ask the engine builder about the main bearing clearances as compared with OEM.