There is a note at the end of Diesel and Shale that implies the additional verse is only sung by Tom Lewis? The verse:

Oh Susie, Oh Susie, Oh won't you be mine?
Submariner's wives have a hell of a time
You'll live like a duchess with cash on the nail
If you don't mind the smell of the diesel and shale
Diesel and shale, diesel and shale,
If you don't mind the smell of the diesel and shale.

is actually an integral and essential part of the song, as it directly precedes and relates to the verse:

Keep walking, keep walking, you foolish young man,
You know that I never would give you my hand.
Your hair is too thin and your face is too pale,
Cause you spend too much time with your diesel and shale,
Diesel and shale, diesel and shale,
You spend too much time with your diesel and shale.

This can be heard on the recording Cyril made of the song on the album Navy Cuts..