Kind of do not see the oil gauge working right until it is running.
Even a brand new battery can be bad.
Check your connections first, then have the battery fully tested at an auto parts store. Where you got it would be the place.
Here is a link for you to check out:
https://www.2carpros.com/articles/everything-goes-dead-when-engine-is-cranked
Keep us posted.
The Medic
Jan 6, 2018 at 9:10 AM