need help guys, my c180 is lately has been having its temperature gauge rises everytime i hit the freeway especially in roads with elevation changes. the temperature drops when i descend or back on a level road. the situation is more severe with the ac on.

i've fixed and replaced

- visco fan
- auxiliary fan relays it's running normal now
- radiator cap

this problem happens at around the same time i had my oil changed.
does engine oils have expiry dates?