Oil pressure drop after change

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2010 Silverado 1500 with 140,000. I switched from Valvoline High Mileage synthetic blend to Valvoline High Mileage full synthetic both 5w-30 and from a Valvoline VO88 oil filter to a Wix Xp. Why did my oil pressure go from 41-42 psi at cold idle to around 28 at cold idle after switching?
 
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1) Synthetic oil consistently performs better in cold than conventional or synthetic blends, even within same grade. Once cooled off - fresh synthetic didn't thicken up as much as used synthetic blend, that is holding bunch of combustion byproducts and contaminants in suspension.
2) How cold? Same cold temp in both instances or slightly warmer now than before?
3) Different oil filter bypass setting?
 
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Jamie86

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I didn't mean cold as in weather. Just starting the truck for the first time that day.
 
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Take Wix filter off. Put another filter on see if that works. Since this just happened after the oil change. Oil pressure is still in spec.
 
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This is a similar thread with similar pressure drops. Do you know this guy?

 
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Oil pickup tube oring is a known problem. Low pressure can occur as the pick-up tube o-ring can suck air where it meets the block.
 
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Not enough of a viscosity change to lower psi. doesn't seem like a pickup tube o ring since it was right after the change.

I can't guarantee but i had that same issue in my 2005 yukon until i changed the oil and filter in the next oci and it went away. Would drop to about 22psi at hot idle and i changed the next time i changed the oil and filter was with another Supertech can i bought at the same time and used the same oil at the time and it went away. Back to around 40psi at hot idle so im guessing it was a defective filter but didnt open it or anything. it was the same brand and bought at the same time. Could just be the filter. Came as soon as i changed the oil and disappeared as soon as i changed it the next time.

Id buy the Acdelco filter just to take the guess work out and see if it changes anything.
 
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2010 Silverado 1500 with 140,000. I switched from Valvoline High Mileage synthetic blend to Valvoline High Mileage full synthetic both 5w-30 and from a Valvoline VO88 oil filter to a Wix Xp. Why did my oil pressure go from 41-42 psi at cold idle to around 28 at cold idle after switching?
Higher-viscosity-index-(VI) oil with about 20% lower cold viscosity combined with fresh oil filter, which is less restrictive on oil and reduces the oil pressure by 5–10 psi so. This is a good thing, not a bad thing. Nothing is broken; so, don't try to fix it.

You can calculate and compare the operational viscosity for the two oils here.


Actually, the oil pressure is driven by the high-shear viscosity, not the low-shear kinematic viscosity (KV) reported on the data sheet. The base-oil viscosity is a better approximation to the high-shear viscosity than the KV. Since you have a synthetic blend versus a full synthetic, the base-oil viscosity index (VI) will be something like 110 vs. 125 or 115 vs. 130, respectively, and you will see even more than a 20% difference in the cold oil viscosity and oil pressure, explaining the cold-oil pressure drop by switching to a better oil, and yes, there is also the less restrictive fresh and larger-capacity oil filter, further reducing the overall, across-the-full-lubrication-circuit oil pressure.
 
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Try oil filter change.
Oil won't make that fifference unless you put 0w 16 in it
 

Jamie86

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This is a similar thread with similar pressure drops. Do you know this guy?

No
 
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search thru some threads on the oil pressure issues related to filters , i have seen it several times , on gm trucks predominantly
 
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I just changed my '04 w/ 5.3 using RGT 5w20, oil pressure is 40 psi hot but up to 50 psi at cold startup, also using Fram Ultra filter. I was leery of running this but read that lots of others are using 5w20 with no noticable difference in wear when having it tested.

Everything seems fine but right now I kinda wished I would've made one change instead of a different oil and filter at the same time, I mostly run Delco filters and have worked out well for me, I figured if it doesn't work out I can just dump it and go back to 5w30.
 
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