My 2008 Boulevard has a digital fuel gauge which looks nice and fancy but works like crap, full for the first 150kms and then drops like a rock for 30kms, I've never trusted it so I just refill every 180-200kms.
My 1982 CB900F has nothing at all except a trip meter, I have yet to run out of fuel on it but when it does I'll just switch the knob over to Reserve and get gas.