Interesting - I used to do the same part time job in `69 - forgot the prices . I worked out a gallon of diesel now is £6.50 so a rough comparison is you need £1 now to buy what a shilling bought in 1970I had a part time job on a petrol station in 70-71. Five star was 6 bob a gallon then.
I've got a bit of faulty memory going on here,
I've just looked up petrol prices, and I reckon the five star was seven bob not six.
Still your 20:1 ratio sounds about right.