I'm usually able to help on questions like this Brian, but didn't 18 undergo a tender change in her career while @ McCloud? That's what might make this difficult to answer unless somebody has a document published by the McCloud of her capacities.
I'd guess 4,000-4,500 gallons on the water and around 1,400 on the oil and that's really just a stab in the dark.
If you look at the profiles of 18 and then 19, you'll notice that 19 has a very short tender, so short in my opinion, that it detracts from her looks. The tender on 18 gives a much more
balanced look, but I do realize that shortlines and loggers did what they felt they had to make things work for them.