Locking gas cap???
 

Hi everyone, new member here with a question. 2003 Silverado 4.8 1500
Last night some person ripped me off of a half a tank of gas, so today I'm going to get a locking gas cap to make sure it doesn't happen again.
My question is this - Is the cap I get a vented one or non vented? They have them both and I'm not sure which one I need.
I'm sure if I get the wrong one the truck will let me know with a "check engine light" and I will have to go somewhere to have it cleared.
Please advise.
Thank you
Rod