Gas is one of the gas stations San Andreas.
It is presented as a very small gas station with a Fire Extinguisher next to it. The gas station is located in Valle Ocultado, Tierra Robada next to the Tee Pee Motel. The gas station of course is not interactive and despite being a gas station, it doesn't have fuel lines, instead it sells gas inside. Most of the time a beater Glendale will have spawned at the back of the block.
Here it is a bigger gas station with some gas pumps near to it. Here you can find a Xoomer-Trailer, too.