I definitely don’t refer to it as a gas station if there’s no gas, but… I may very well refer to the convenience store attached to the gas station as a “gas station”. Like “I’m gonna stop at a gas station and get some coffee”, even if I mean any convenience store, gas or no.

It’s like a rectangle-square situation

I've noticed it's less common in the city and more common in rural areas. I live in SF and people here don't call them gas stations unless they have gas, but in the Central Valley this is extremely common.

I grew up there and I always forget how much more "proper" I speak at home vs where I grew up. My partner sometimes struggles to understand what I'm trying to say a lot of the time when I slip back into it when speaking with my family. Gas station is just one of the many overly generic terms. Another one is "Vallarta" which doesn't necessarily mean the chain grocery store Vallarta, but a Mexican grocery store usually selling produce and with a meat counter.