Oil Pressure Change

[EastTNChevy]

I have a question that I’m hoping someone can help answer. I have a 2008 Silverado with the 5.3 and 39K miles on it. Up until now I have always taken it to the dealer for oil changes but I decided to do it myself a couple days ago. They used conventional oil with AC Delco filter. I put Mobil 1 synthetic and a Wix filter back on it. Before this my idle oil pressure was 20 PSI and cruising was 40 PSI. Now, however, my idle is like 35 PSI and cruising is around 50 PSI. Any idea why the change?

[dtnel78]

Welcome to synthetic oil. In this day and age I'm sure the dealer was using a synthetic blend as most or all vehicles from 08 or somewhere in there recommended at least a blend. Now that you have the synthetic in there you'll want to stay with it as they don't really recommend switching back and forth once you upgrade to synthetic oil. 

 

The filter may be a better flowing filter but not 100% on that as I don't follow them that close enough to know for sure  

[sefiroxx]

Better oil, better filter, better results.

[Mikebtte]

Because dealers give you cheap oil. Welcome to the world of quality oil. All the dealer cares is that you make it pasted warranty.

Try some high quality oil and you will see even more gains.

I ran Schaeffer and saw an extra 10 PSI over other oils. I was relatively surprised.

[dennismc]

I have been running Mobile 1 oil and filter on my 08 since almost new. My oil pressures are exactly same as yours.

 

[swathdiver]

On 12/31/2019 at 5:29 AM, EastTNChevy said:

I have a question that I’m hoping someone can help answer. I have a 2008 Silverado with the 5.3 and 39K miles on it. Up until now I have always taken it to the dealer for oil changes but I decided to do it myself a couple days ago. They used conventional oil with AC Delco filter. I put Mobil 1 synthetic and a Wix filter back on it. Before this my idle oil pressure was 20 PSI and cruising was 40 PSI. Now, however, my idle is like 35 PSI and cruising is around 50 PSI. Any idea why the change?

Mobil 1 has lower (thinner) viscosity numbers compared with ACDelco's synthetic or synthetic blend oils.  Your truck originally called for the synthetic blend which has been upgraded to full synthetic, especially if you have the LC9, aluminum engine block.

 

M1 is fine but I prefer the new full synthetic ACDelco oil, less noise on start up.  10-9234/10-9147  The new Shell Rotella Gas Truck is very similar.