Manual calls for 10W30 API CD SE. If I understand correctly, API CD (diesel) and SE (automotive) are both obsolete codes. I spoke to Thomas yesterday and the tech on the phone (Brian) suggested that I use the best API grade diesel in the engine and the best API automotive for the hydraulic and final drive boxes. From what I understand, the best API diesel for this Kubota (4 stroke?) V1903B is CG-4 and current API rating for automotive is SH. In the best of all worlds, I've find something reasonably priced that was both CG-4 and SH, but I haven't had any luck yet. In round numbers this machine takes 13 gallons of oil - (engine 2 gallons, final drives 3 gallons and hydraulic 8 gallons). Questions: 1) Does it sound reasonable to use 10W30 SH only in the hydraulic and final drives - i.e. the oil will not have any diesel rating? 2) I'm thinking about a high quality synthetic for the Kubota V1903 engine (1719 hours). This oil will most likely be CG-4 and SH, but sadly unaffordable for the 11 gallons necessary for the final drives and hydraulic system. Any reason I wouldn't want to switch to synthetic for the engine? 3) Any hope of finding a high quality (most likely non-synthetic) oil for a reasonable cost that is both CG-4 and SH? Thanks!