Hello all, I'm looking for some recommendations on the intervals to change the engine oil and the hydraulic/transmission fluid. Is that bases on hours in use, or once a year, etc.? Thanks in advance.

Here are some pages from the OEM 8N Operator's Manual for the lube and maintenance schedule. If you don't have all the manuals, there are some in the forum here you can download. Oils stated were different back then but Bruce(VA) listed modern versions to use.

Annually on the oil ( 15w40 Rotella) and every 3-5 years on the hydraulic fluid, depending on its water content! ( UTF from TSC)

Thanks Bruce! Two follow up questions to that. 1) I’ve been running 10w30 for a few years now…is that bad? 2) Is there an easy way to check for water? Just check the dipstick?

There are but two criteria you need to consider when buying engine oil : the operating conditions of the tractor ( the ambient temp) and that it needs to be multi-vis. So consult a viscosity chart. Brand is not critical; any multi-vis detergent oil appropriate for your climate conditions will work perfectly well in your tractor. Unless the tractor is never operated below 32* F, do not use straight weight oil. And do not add zinc; the modern oils have all the zinc a tractor engine needs. I use 15w40 Shell T-4 Rotella in all the old tractors and old cars year around here in VA.

Just look at the color of the hydraulic fluid on the dipstick. If it looks like a milkshake, it's water-logged.

Great, thank you very much!