oil use and head gasket

I was thinking -- our higher mile Prius 214k. Started to use a bit of oil as it aged ... let say around 125k we noticed could no longer go the full 10k w/o putting some in.

At some post further on it was using more oil .. let's say 160k ... then it actually stopped using as much ... it was using oil maybe 1qt in 3-4k or so ... but prior it was using more. I would have to top it off -- I did not monitor it down to the exact miles. We check all our cars often and they get topped off.

I'm wondering how much the EGR circuit has to do with this -- do you think as the cooler starts to clog and no longer cools the gasses -- this higher heat actually causes the heads to overheat and use more oil? I would think this would cause oil vaporization through the PVC valve as well .. also using oil .. into the intake.

As the system clogs further -- the gasses can't flow and the heat is eliminated and the oil uses now drops?

It will be interesting to see how mine operates with the fully cleaned intake and new valve and cooler -- we just put about 500 miles on it with lower than normal MPG 45 .... but the driver never gets good MPG. No coolant use .. it was not using coolant prior to the codes.