Most of the major oil suppliers can give you an comprehencsive lubrication selection recommendation from their various products based on your needs. Try to make a connection with their lubricant engineer or technical group as opposed to dealing with a local salesman/distriutor. I would start with the OEM recommendations and make an application list and have the prospective suppliers submit their recomendations for each application with costs per gallon and a detailed spec sheet showing lubricant parameters. Most suppliers will not provide detailed info on the additive package but when you decide on a vendor you can always do baseline testing to determine element concentrations. Price is not an indicator of quality or suitablility.

the TOST test uses a kind of useful life test for turbine oils (that usually do not contain a oxidation inhibitor or antiwear additives), the test is therefore unsuitable for hydraulic oils or gear oils.

gear oils and hydraulic oils can vary quite a bit in performance, depending on basefluids and additives used. the performance can to a certain extend be judged based on the FZG test and various tests as required by hydraulic equipment manufacturers. most suppliers can supply a range of products that differ in performance, composition and price.

as suggested, the best starting point is to talk to a technical representative who will be able to inform you about the performance of the various products offered which might assist you in ranking the various offers.

it may also be possible to get a longer life of the fluid when buying not the cheapest variety which in the end may well be cheaper because you will have less downtime and less waste that has to be processed afterwards. you should realize that it is not the initial outlay only that constitutes the cost, but also the life expectancy, the cost of getting rid off it afterwards, down time, labor costs and eventually the cost of repairs. the cost of the fluid itself in the end is not the most important element in getting the cost per hour or unit produced as low as possible.