I'm going to cut traffic on the shoulder to get gas
What does it mean to cut traffic?
I'm going to change lanes immediately without signaling my intentions.
I think that you should follow the rules of the road. You could get really hurt or somebody else could. You could also get fined and I wouldn't want you to spend a lot of money on one careless move.
I'm only doing this to be more efficient.
It wouldn't be very efficient if it caused an accident and then you would be delayed even more. You should do your best to follow the rules and if need be leave early so that you can still make it in on time.