I spoke to my mechanic today and he said u dont have to have a vent cause most new batterys are sealed and not like the old ones where they had screw caps on top and acid would come out. I had a look at my ve sv6 wagon tonight it don't have one although the grommet was there and my acdelco battery had both holes. Why wasn't it fitted from factory if this is so important????
Your mechanic is incorrect, and it is important to vent the battery, especially in a VE/VF.
The smart charging system pumps the voltage back to the battery after starting, and the battery will gas.
And because VE/VF sedans, wagons and utes all have the battery mounted within the passenger cabin, it need to vent externally.
I've seen pics of a week old SS ute, that had a kink in the vent tube, and the battery burst from the pressure build up.
The ute was written off.