do i have to change oil after replacing intake manifold gasket on 1998 GMC Sonoma

oil was recently changed

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2 answers
Anytime you change the intake manifold gasket it is always a good idea to change the oil becuase of the possibility of antifreeze getting into the oil via your valve rod catches at the bottom of your intake if it is not sealed properly.
I have a 2000 suburban and I need the intake manifold gaskets replaced--Getting lean codes P0171 and P0174-- the Mechanic says that I am going to need to replace the oil after replacing the manifold. I was under the impression that it would be antifreeze not oil in the intake manifold.