You all get to choose.. Do you want to be cheap, and get non-detergent motor oil,
and abuse the rods and bearings in your pump, and take the risk of Quickly overheating the seals in your pump ?
..Just to say you found the cheapest way to introduce UnNecessary DownTime in your business?
Or, use a good "Gearbox" Oil .. Synthetic is Best, and in summer.. 75w-140