Fuel dilution in lube oil when analyzed by a competent lab like Blackstone for instance is a sure sign of either worn rings or injector issues, neither of which I have with either of my pre-4 Kubota M9's and why I'd be very hesitant when buying a used machine, especially one with excessive hours on it and / or no supplied with maintenance records. My OS M9, I bought used from a JD dealer of all things, but it came with not only the original owners manual and the shop manual (which I didn't need because I already have one), but it came with dated service records, right down to the brand of lube oil and gearbox oil installed as well, plus all the filters had the change hours painted on them in paint pen, which is something I do as well as it gives me a quick visual reference as to pending service time. In reality I would not be at all hesitant to purchase a post 4 tractor if I required one, which I don't as both my pre 4 tractors run flawlessly but I would wait until the manufacturers work all the bugs out of them and in my case, for the power I require, they would not only be SCR units but DEF injection as well. I believe under EPA mandate, any unit in the excess of 90 stub pto output requires DEF injection as well as Selective Catalytic Reduction (SCR) or what is now present on units above 26 stub (pto) horsepower. Keep in mind that tractors are rated (for emissions compliance with stub (pto) horsepower, not flywheel horsepower. Motor vehicles such as cars or trucks are rated at flywheel output, which is always greater than driveshaft power, usually 10% more. 10% is the rule of thumb used to take into account parasitic loss in the transmission and hydrostats are usually more than 10% as a rule because of the fluid coupling (hydrostatic drive). In my applications, where I require maximum output at times, a hydrostatic transmission won't work, I must have a conventional gearbox. The one thing I don't want is a dry clutch because many times I'm operating in a 'half clutch' situation, consequently I run tractors with wet, multiplate clutches that are basically immune to clutch plate wear from half clutch operation. My goal is to always have tractors with NO dry clutch in the bellhousing and that is exactly what my hydraulic shuttle Kubota's give me.
I can literally 'ride' the clutch pedal all day and not wear the clutch one bit. Not that I do but I could if necessary. Even with a hydrostat, you will have a dry clutch in the bellhousing that will eventually need replacement and that replacement entails splitting the unit. I don't have that issue with the hydraulic shuttle as all that is in the bellhousing is a damper plate connected to the crankshaft output flange and another plate connected to the transmission input shaft via a set of radial coil springs with the sole purpose of dampening the shock load imposed by abrupt directional changes and even those are mitigated by the proportional hydraulic valving that controls the 'lockup' pressure on the wet clutch pack that drives the gearbox and transmits power to the wheels and eventually, the ground. In reality, it's a very well engineered system that operates flawlessly and eliminates the dry clutch entirely and the hydraulic actuator valve on the side of the main gearbox also maintains optimum lockup pressure and it adjustable if required. it does require a special fitting and liquid filled pressure gage to check but I have that and when I check it, it's always within Kubota listed specification for correct lockup pressure, even on my 6000 plus hour machine.
I believe JD also offers a similar setup but they call theirs a 'power shuttle' transmission.
