saifi don't bother taking it to a mechanic, just get some hard plastic beads (like the ones used in bead blasting) and 1/4 fill the tank with them. give it a good shake for a few minutes and then rinse out the tank with fuel. repeat this process a few times and you'll have a clean tank.
Mechanics only put in some diesel and shake it,... that only gets rid of SOME surface rust.
