so did all the manufacturers of lubesters adhere to this rule of thumb? that if you make a lubester tank one inch of depth equals one gallon. and the theory that they used inches in case you lost the dip stick. then the dip stick would say gallons. and if you lost it you would know to use a stick or a 3 ft ruler and every inch is a gallon. this will bug me until i put a gallon of water in it tomorrow. i wont sleep to night.
moonphone: in my experience, most product whether it be gas or oil was dispensed in a defined unit of measurement like a quart or gallon.
Inventory however was usually measured in inches. If you had a square tank and you knew how many gallon capacity it was...say a 25 gallon tank...you just checked how many inches were left and you knew when to reorder.
Over the years the size of bulk oil tanks became larger with manufacturers like Aro adding air pressure...but even then most of the garage owners I knew had a wooden measuring stick and they would 'stick' the tank to see how much product was left. Eventually gallon meters were installed on top of the tank so you could see how much product was left in gallons.
Gasoline was the same way, the product in the tanks were measured in inches. We would have to 'stick' the tanks every night. You also have to take into account the shape of the tank. The larger storeage tanks were not square..but cylindrical. Once you determined how many inches were in the tank you looked at a chart that would show you how many gallons there were.
Yours was a good question, got me thinking about how tightly controlled the dispensing of product was, but in reality inventory management wasn't nearly so. Hope that helps some.