The following Bulk Fluid vehicles have no stated capacity and therefore appear with the other tractor units even though they are unable to tow a trailor, and therefore have no use in game unless I'm mistaken.
Leyland T45 Constructor
Leyland DAF 85 Rigid
DAF CF Rigid
Edit:I'm using Pak.Britain Standard version Compiled up to Revision 230 the most recent I could find on Sourceforge
Thanks for the report. The dat files seem to be missing their freight capacities lines. I will restore these and fix for 1.06.
Edit: fixed in SVN r238