Painted on metal Purolator filter sign. Circa 1960-70s.
 
Dimensions: 75 x 50cm
 
The company was founded in 1923 as Motor Improvements, Incorporated in New York City. The company's Purolator (initially stylised PurOlator and sometimes Pur-O-Lator) oil filtration device, invented in 1922 by Ernest John Sweetland and George H. Greenhalgh, was standard equipment on early 1920s Chrysler automobiles after being launched on the Chrysler Six.The name Purolator was a portmanteau of pure oil later.
The Purolator was the first modern automotive oil filter and reduced the need to flush a car's crankcase to clean out oil contaminants, at the time a regular and costly maintenance item.
The company later changed its name to the name of its most well-known brand, Purolator Products, Inc.
 
source: https://en.wikipedia.org/wiki/Purolator_Filters (citations removed and edited).