After looking at some of my stored notes, I found the Energee trademark from 1923. I know that "True gasoline" was used prior to 1921, but I can't find in my online stored pictures of the use of the car in any pre-1921 ads. I have more stuff at home I can look at, but i'm away for a few days. I'll take a look when I can and provide more info. I think its safe to say your sign is from roughly 1920-1922. The use of the yellow and black leads me to think it was either from the Pure Oil company of Minneapolis, or immediately after PO of Ohio purchased them.
My 2 cents at this point.
