'04 Tahoe, 85,000 miles, Mobil 1 and good filters used since new. Always changed at about 4500-5000 when color changed. Lab test showed Nitration is at 23 and in the low end of the abnormal range. All other levels are normal and truck runs fine. But, could the PCV-EGR system not be working to remove the blowby (if any) ? Thanks. *BW*

 

The EGR system isnt designed to remove all NOx from combustion only to limit it into the atmosphere.

PCV is solely meant to burn excess hydrocarbons.

This is why they use the Cat. Conv. To convert the HCs to H2O and CO2..

Besides the low end of abnormal from the motor oil? No one measures that they all measure at the exhaust pipe.

 

Minor nit to pick: EGR doesn't remove NOX, it prevents it from occurring by lowering the combustion temperature.

Not sure what nitration in the oil indicates. Maybe the lab he used can shed some light.

 

Nitration, I believe contributes to a break down of the oils viscosity

 

That's not good.