Hiya Dave,
I have an answer to your question.
I spoke with Charlie Brennan today who owns the former Texaco (now Exxon) bulk plant in Durango. The Brennan Family has been in Durango forever. I believe that it was Charlie's grandfather who opened the business. He said that it was the POWERINE bulk plant. Owned locally by John Keeling.
Here's what I found on POWERINE:
Powerine was based in Denver. They were purchased by a Standard of New Jersey subsidiary in 1938(?) or 1945 per another source. The Powerine name was kept until after World War II, when they changed to the Oval-E name. The Oval-E logo is strikingly similar to Esso and Enco and many other brands which were owned by Standard of New Jersey.
Most of the above information from "Guide to Gasoline Logos"
by Wayne Henderson and Scott Benjamin.
The below Oval E example is from 1949.
Ray Loose
Durango, Colorado