Back in 1960s, 1 oz of silver can buy 4.5 gallons of gasoline. (31c junk silver per gallon) Over the last 50 years, it seems this ratio stay roughly the same; excluding the years when silver spot spiked. This year the US national average gasoline costs about $2.60 per gallon; if using the multiple of 4.5 (historical norm), we should have seen $11.7 per oz.
Just another way to calculate
Just another way to calculate