Your tractor can use any diesel fuel. I'd be really surprised if you could find high sulphur at all. You might find dyed low sulphur(500ppm),but it's really being phased out fast. You're most likely getting ultra-low sulphur(<15ppm)in either dyed or undyed. Sulphur is a lubricant for the fuel system,so it is desireable,however oil changes can go longer if less sulphur is in the fuel. Since you really don't have a choice anymore,just assume you're getting ultra-low and consider a fuel additive for lubricity,although I believe there is a lubricity standard that fuel suppliers have to meet. Or just put it in and don't worry about it except for cold weather treatment. Good Luck