Hi,
You can slow down the effect by going to the attribute editor, Dynamic simulation and changing the simulation rate scale to a smaller number, as 2.5 is 2.5 times faster, so it would last 2.5 times shorter, I think it is like a scale on time (but not definate) so it shouldn't change the sim look, and u can pre roll your simulation so it looks good at frame 0 by changing the start frame to say -50 (and your time slider).

I assume you have a burst of fuel in the container, which is then being used up, u may have to go to the fluid emitter and crank up the fuel emisson rate, or maybe keyframe it

AnDy