I have a tractor business in which I use a 1973 574 international tractor with a D239 engine. It has only 1950 hours. I change the Hydraulic Transmission Fluid(HTF) every 500 hours because of the hard work involved in my work. I have been buying the Cub Cadet HTF at a high price and don't want a cheap oil in it. Someone suggested using an another named brand of HTF. Has anyone got ant suggestions on a cheaper but good HTF oil Thanks Bruce