Yes, the drain plug is 15/16, the torque on the drain plug is 30 foot lb's, there is a fiber washer that goes on the oil pan drain plug, I would recommend replacing it every oil change. Their cheap insurance. There is one oil filter, one primary "drop in" fuel filter, these are the filters you would change at a normal PM interval. Be sure to fill your oil filter before you install it and i would recommend only using HINO brand fuel filters. The cheap ones have a larger micron rating and will allow larger than intended debris into your injectors and oil system, There are however additional filter that need to be replaced. The DEF filter at 150k (in the def pump), Crankcase breather filter (on top of the valve cover) at 60k, If you have air brakes I recommend replacing the air drier cartridge every 2 years. There is a secondary fuel filter or "bubbler filter" (black filter mounted on the rh side of the engine) that has a recommended replacement interval of 84 months or 240k miles. That interval is ridiculous in my opinion, so I advise to replace them at 100k or every 2 years minimum. We have crappy fuel up in the northeast. The oil capacity is 16 quarts. The transmission has different intervals depending on what one you have. I would suspect you have the 2k Allison with the external spin on filter. I have attached a PDF of the recommended PM items for reference. If at all possible pay a shop to show you how to do it, then you will know how its done. If your not careful you can create a problem. I see cut o-rings, missing o-rings, triple stacked washers, all kinds of weird stuff. Get an owners manual and read it, you will save yourself a lot of headaches. Hino makes a a great owners manual with all the info you would need to perform a quality PM.
Out of curiosity, what weight oil is recommended for these trucks? I have been using the chevron delo 5w40 synthetic in our trucks and changing it every 10k miles. We operate the trucks as rollback tow trucks.
From the 2015 Conventional owners manual. Not sure what year/years you are running look on the bottle to verify it is CJ-4 aproved. "
Use of API CJ-4 grade engine oil is recommended to achieve optimum performance of the DPR."