Not my area of expertise. 

But, I’m running the Mobile 1 15/50 and also I believe have 80 PSI at cold start. 

You introduced two variables so you need to make one go away to be sure.

I’m guessing it it is the position of the sensor.

Eric Caron 
85 GL Auto 

> On May 10, 2021, at 11:43 PM, Gene P <olgreywoof@gmail.com> wrote:
> 
> Hey folks,
> 87 Wolfsburg 2.1, original everything
> I don’t think this is a problem, I’m just wanting to learn something.
> For years I’ve had VDO oil pressure and temp gauges, senders on a sandwich adaptor at the oil filter.  Start-up pressure has been just under 80, right at the top of the gauge, in any season.
> 
> As part of a recent project, I pulled the sender between the pushrod tubes and put that with the VDO sender on a tee about 7 inches forward of that port.  Now start-up pressure is about 55-57.  Would moving the sender in that manner cause a change, or that much change, in the reading?
> 
> The other change I made (burying the lead I think) is switching from Castrol 20W/50 to Mobil1 15/50 for the first time.  Does synthetic oil make that much difference in start-up pressure?