Lubrication questions on a '51 DC-3

What oil (weight/viscosity) should I use in the engine? In the hydraulic system? Is there seperate oil for the rearend/drive axle or is it using engine oil as well?

I know how to achieve the proper oil level in the hydraulic system but how do I do it in the engine? Rear axle?

Lastly, what weight/viscosity of oil should I use in my air cleaner/oil bath? If I am mowing grass with this thing do I really need to change the oid in the air cleaner every day I use it?

Use engine oil in air cleaner. I don't change mine very often as someone had fitted a paper element car type filter on the top of the airintake pipe so I am not a typical example.

For Trans use 90w There are two drain plugs one near belt pulley one further back. 10.5 gallons fill until it runs out the level plug on the right side of Trans housing.

PTO Hydraulic (Live PTO)
Originally called for 10w but in the 50s the PTO clutches were redesigned and then specified Dexron/Type A ATF about 10 qts fill to the level plug on the left rear of housing.

Note the Tran fill and PTO fill are close together be careful (Speaking from!painful experience !!)

Chris