Oil pressure drop after oil change

[Jamie86]

2010 Silverado 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?

[richard wysong]

it wouldnt be the filter so it must be the oil, 

[dna9656]

Are you sure this IS the correct filter for your application, sure the filter is on tightly? Did you put the oil pan drain plug back in and properly (read not over tighten but to the spec.?) tighten it? Did you check the oil lever after filling (this ensures the oil is in the pan and not on the ground) but prior to engine start?

Stranger things have happened!

[richard wysong]

Filter will NOT affect op. most of the oil bypasses the filter, the things that affect op are oil viscosity, oil pressure relief valve and bearing clearances. also restricted pickup screen. try changing back to the oil you were using and see what happens, maybe the oil was labeled wrong

[Black02Silverado]

Just curious as to what is the part number of the Wix oil filter you installed?

[customboss]

Normal event. Less resistance to flow. 
If your ambient temps are colder than the last time you observed cold start oil pressure you are also seeing pour point depressants in action keeping oil at 5W for crank and start pumpability. 
The chemistry of the valvo blend vs full syn are dramatic in colder ambient temp ops. 
Regardless it’s not a bad thing.
Your normal operating temp oil pressure may be lower too. Also not a bad thing unless below normal pressure for the oil pump.  

[Grumpy Bear]

Visual of above comment: 

Same viscosity at operating temperature but much different on cold start up.

 

[Jamie86]

On 11/12/2021 at 12:07 PM, Black02Silverado said:

Just curious as to what is the part number of the Wix oil filter you installed?

57060xp 

[Supreme Pizza]

Seeding much?  The poster knows what I mean.

[Jamie86]

On 11/14/2021 at 1:43 AM, Supreme Pizza said:

Seeding much?  The poster knows what I mean.

No I dont.

[redvett]

In my of 50 years as an ASE certified tech i have seen a fare share of bad oil filters and if the oil is the same viscosity regardless of mineral or synthetic oil the oil will not change the pressure its always the oil filter. Under normal operation the oil filter passes 100% of the oil through it but when the filter becomes plugged the bypass allow oil by the filter lowering the oil pressure.  Change the filter its easy and cheap.

[richard wysong]

i disagree, the oil pump makes enuff pressure to explode a filter, if the bypass valve didnt work you would have hundreds of lbs of op. high performance pumps have changable relief valve springs to adjust desired pressure. I have also been a tech for almost 50 years and built my own race engines

[elcamino]

Oil pressure is directly related to resistance to oil flow.  Because of the lower resistance to flow that synthetics offer, the oil pressure will generally be reduced as well.  Lower resistance to flow also means less friction and potentially better power or efficiency.

[richard wysong]

EXACTLY!!, thank you ElCamino