Looks like a LIFE magazine shot of the period.
I like this photo. It dates the Mobile Horse license plate topper. I have one of those on the license plate on my 1931 A roadster. It is nice to know that I am not too far off in the use of it on my A.
Actually the red Pegasus was not associated with Mobil oil when this picture was taken. In 1933 the Pegasus emblem was the logo for the Magnolia Oil company of Dallas, Texas.
Magnolia Oil was founded in 1911. It was purchased by Standard Oil in the 1920's but continued operating as Magnolia. Standard Oil of New York (SOCONY) was eventually purchased by Mobil during the Eisenhour administration. Mobil adopted the logo and replaced the Magnolia signs with Mobil signs during the Kennedy administration.
Here is the Pegasus on top of the Magnolia Petroleum building:
I don't know the history of Mobil and the Pegasus trade mark in the USA, but Exxon Mobil (Esso) has a very informative web site here in Australia.
Mobil, as a brand name and even with some merges like the Vacuum oil Co and then Colonial Oil Co, has operated in the south end of the globe for over 115 years.
Mobil introduced the flying Red Horse (Pegasus) logo, first appeared in Australia in 1939.
I did find this article on a US site, as the tin says Socony Vacuum Oil Company.
From the looks of that photo, I'd say they are already in California!