And many/most controllers say/used to say: ''PLEASE STATE TOTAL FUEL AND SOULS ON BOARD'' ... thus providing a further 'headwork' complication to an already potentially 'complex' problem ... I always told 'em to ''STAND-BY'' w/ the head-count if we were procedure-buried at the moment (can't they check w/ company ??? we'll get to it when we can--it's easy w/ a Second Officer, but he's probably reading the EMERG Checklist ... ) ... but the fuel ... ahhhhhhhhhhh .... there's that fuel 'thing' again. That one's 'easy' ... you should KNOW it alla' de' time ...One thing to throw out from experience as well as to ask the others with lots of commercial experience is that everytime I have had to declare an emergency, the controller has thrown in the, "When able state the nature of your emergency.".... It also let's the controller pass on to the field what is happening and even though sending emergency vehicles is standard, maybe you had a fire that injured 30 people. Two ambulances ain't gonna help much.
While the e-word can be used to give you options...
You've got quite a few options w/out declaring an 'EMERGENCY'. I've asked Tower/ATC to ''ROLL THE EQUIPMENT'' when I had a 'problem' that may or may have not eventually included bumping it up to 'EMERGENCY' status -- that's what the guys in the fire house are getting paid for, and most of 'em wanted 'something to do' in any case. I figured it was more prudent to have a couple of OSHKOSH's following us during the roll-out/back-taxi than to have the 'problem' deteriorate and have no emerg/crash assistance readily available ...
Never caught any flak for 'rolling the equipment' and ultimately not 'needing' it, and neither did any of my Amigos. It's part of the job.