An accomplished painter, whose watercolors grace the covers of some of her books, Elizabeth Bishop is very much the pictorial poet. "Oh, but it is dirty!" the opening exclamation presents the picture of a grease and "oil-permeated" gas station that appears to display not only carelessness, but neglect--"Be careful with that match!"

That the owner and his sons are equally as slovenly is indicated by father's "dirty oil-soaked monkey suit" and the son's greasy clothing. Appalled by all this oil and grease, the speaker wonders if they live at this station as she notices

a set of crushed and grease-
impregnated wickerwork;
on the wicker sofa
a dirty dog, quite comfy.

and wonders at the feminine touch in amid all this grime: "Why, oh why, the doily?"  But, it is at this point that the speaker comes to realize that, albeit "oil-soaked," the filling station has the makings of a home. For, beneath the grime, there is evidence of unity as the sons have probably fingered through the comic books while sitting on the "impregnated wickerwork" as a dog--himself covered in grease as one of the family--lies contentedly upon the wicker sofa. 

The "hirsuite begonia" suggests a love of beauty amid the toils of the men at the station, Further, "somebody"; namely, the wife and mother, tends to this hairy plant, connotative of the men, and lays a doily lovingly under her sons' comic books. These pivotal details project the speaker into the realization that "Somebody loves us all" and even in greasy filling stations there can be loving relationships.

How does "We should not judge by appearances" apply to Bishop's poem "The Filling Station"?

“The Filling Station” by Elizabeth Bishop elicits the speaker’s need for her mother. The tone of the poem varies from stanza to stanza. The poet is disgusted by the dirt, yet this is her home. In this intriguing poem, the author proves the statement that one cannot judge anything or anyone by its appearance.  There is always more to see and understand.  

1st stanza

The speaker describes a roadside filling station. This kind of facility is almost extinct.  In the past, the servicemen filled the tank, washed the windshield, checked the oil and the air in the tires.  It has been replaced by the unfeeling “get and go” businesses devoted to taking the person’s money and forgetting any personalized service.

Oil and grease permeated  this little filling station. When something is touched by the oil, nothing is done to clean it up. To the first person unnamed narrator,  this station is disgusting. She sarcastically notes that a person better not light a match for fear that because of the oil everything might go up in flames.

2nd stanza

The narrator attempts to make the poem impersonal; however, the first word of this stanza lets the reader know that this girl’s father is the owner of the station.  The father is a mechanic because he wears a monkey suit [a grease monkey is a colloquialism for auto mechanic].  His overalls are too small; he has not taken the time to buy a larger size. The sons help him at the station. The narrator describes them as fast yet sassy---this station belongs to the family; due to the work, all of the men in the family are dirty.

3rd stanza

The narrator asks the question---where does the family live?  Do they stay in the station itself. There is a porch with oil covered wicker chairs---probably where the boys sits in between their work.  There is a dirty dog who sits comfortably in one of the chairs.

4th and  5th stanzas

This verse changes the tone and impetus of the poem.  Inside the station, there is a special place. The comic books give color to the place.

The doily is important because someone made it and places it on a little table beside a bushy flower. The narrator asks why the plant and table are in this place.  She is particularly drawn to the embroidered doily that has been made by someone with loving hands.

6th  and 7th stanzas

 Somebody
Arranges the rows of cans
So that they softly say:
Esso—so—so—so
To high strung automobiles
Somebody loves us all

There was someone who made the doily and watered the plant. There is a person that arranges the cans in a special way.  Obviously, there is someone who speaks softly with love toward the  family.

As the poem progresses, the attitude of the narrator changes. Someone loves us….not someone loves them.  She now takes her place as a member of the family.  The author lost her mother at an early age.  It is easy to assume that the narrator is longing for her own mother who loved her.