Interestingly not mentioned here is that tractor oils, which includes UDT and SUDT, are not lub oil and not hydraulic fluid. I can offer some insight, since I work for a large hydraulic company.
Lub and gear oils are not suitable for hydraulic applications. High pressure, foaming, additives and other factors define the differences. Hydraulic oil variants like ATF, are good enough lubricants to use for gearboxes, as in automatic transmissions. Problem in tractors is the brakes. The multi-plate brakes (and clutches in some) requires that the oil have some characteristics to not be "too slippery", and to be able to take high temperatures without breaking down. Also brake wear material will be present in the oil and must be compatible with the fluid. This limits ATF as the best oil for tractors. The last factor is a viscosity index that prevents the oil from becoming too thin when hot and too thick when cold.
Most oil varieties "will" work in a tractor, but be less than optimal. SUDT seems to be a high grade tractor oil with regard to these factors. I suspect that UDT is more of a standard tractor oil, but the likelihood of extended use in very cold applications (snowblowing) may have been the basis for improving beyond UDT.
I would be hesitant to use ATF in the tractor. A good tractor oil should be fine, but may not have as desirable characteristics when cold as SUDT or other high performance tractor oils.
paul
Lub and gear oils are not suitable for hydraulic applications. High pressure, foaming, additives and other factors define the differences. Hydraulic oil variants like ATF, are good enough lubricants to use for gearboxes, as in automatic transmissions. Problem in tractors is the brakes. The multi-plate brakes (and clutches in some) requires that the oil have some characteristics to not be "too slippery", and to be able to take high temperatures without breaking down. Also brake wear material will be present in the oil and must be compatible with the fluid. This limits ATF as the best oil for tractors. The last factor is a viscosity index that prevents the oil from becoming too thin when hot and too thick when cold.
Most oil varieties "will" work in a tractor, but be less than optimal. SUDT seems to be a high grade tractor oil with regard to these factors. I suspect that UDT is more of a standard tractor oil, but the likelihood of extended use in very cold applications (snowblowing) may have been the basis for improving beyond UDT.
I would be hesitant to use ATF in the tractor. A good tractor oil should be fine, but may not have as desirable characteristics when cold as SUDT or other high performance tractor oils.
paul
